Single-pass, heavy ion systems for large-scale neutron source applications

ABSTRACT

A single-pass heavy-ion fusion system for power production from fusion reactions alone, power production that uses additional energy of fission reactions obtained by driving a sub-critical fission pile with the neutrons from fusion reactions, destroying high-level and/or long-lived radioactive waste by intense bombardment with fusion neutrons, or for the production of neutron beams for various applications includes a new arrangement of current multiplying processes that employs a multiplicity of isotopes to achieve the desired effect of distributing the task of amplifying the current among all the various processes, to relieve stress on any one process, and to increase the design margin for assured ICF (inertial confinement fusion) ignition for applications including but not restricted to the above list. The energy content and power of the ignition-driver pulses are greatly increased, thus increasing intensity of target heating and rendering reliable ignition readily attainable.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.15/081,768, filed Mar. 25, 2016, which is a Continuation of U.S. patentapplication Ser. No. 13/482,922, filed May 29, 2012, now U.S. Pat. No.9,299,461, issued Mar. 29, 2016, which is a Continuation-In-Part of U.S.patent application Ser. No. 12/484,004, filed Jun. 12, 2009, nowabandoned, each of which are incorporated herein in their entirety thisreference thereto.

U.S. patent application Ser. No. 12/484,004 claims the benefit of U.S.Provisional Patent Application Ser. No. 61/061,593, filed Jun. 13, 2008,the entirety of which is also incorporated herein by this referencethereto.

BACKGROUND OF THE INVENTION Field of the Invention

In a general sense, the invention is related to systems achievingnuclear fusion reactions at large-scale for economical generation ofpower by fusion reactions only, generation of power by drivingsub-critical fission piles with neutrons from fusion reactions, andproduction of neutrons for other applications including but not limitedto pulsed neutron beams for research, medical applications, etc. Inaddition, the techniques for generating ion beams needed to ignitefusion may be used together or singly to increase the intensity of ionbeams for various applications.

Background Information

The heavy ion driver defined in 1975-1976 by R. L. Martin and A. W.Maschke used the known abilities of high-energy RF (radiofrequency)accelerator systems to store megaJoule quantities of ion beam energy andto focus this stored energy on very small spots. They saw that the shortstopping distance of beam nuclei with high atomic number (Z) atapproximately one-half the speed of light meant being able to create theenergy density in small targets containing fusion fuel that is needed toignite small clean-fusion explosions. And they showed that thecontinuous stored beams could be rearranged into multiple bunches,compressed in length, and delivered to the targets in short durationpulses as required by the dynamics of the fusion ignition and burnprocesses.

Beams of protons can be accumulated—and stored—over a long period oftime, as the protons resist processes that cause them to wander fromtheir controlled paths, such as knock-on or multiple scattering, andhave low probability of changing their charge to O (neutral) or negative(H−). On the other hand, the probability of the charge state of a heavyion changing by collision with an atom remaining even in a very highvacuum requires ignition pulses be generated in a fraction of a second.This is consistent with the need for an ICF (inertial confinementfusion) power plant reactor to pulse frequently, and pulsing many timesper second is routine for accelerator systems. However, the need togenerate an ignition pulse within a limited time places a constraint onthe accelerator technology that eliminates slow pulsing machines likesynchrotrons.

Thus, at the inception of heavy ion fusion (HIF), a few principles wereestablished:

-   -   GeVs of energy in each ion provided means to generate beam        pulses to ignite ICF burn with: much more total beam energy than        competing technologies, the tight focusing required by the        dimensions of fusion fuel pellets, the beam power required for        ignition with beam currents obtainable with confirmed processes;    -   Rearrangement of the total beam for an ignitor pulse into the        short time duration required for the fuel compression and        ignition processes is the technical issue;    -   The question for economics is the cost of large particle        accelerators, which does not fit conventional ideas of electric        power generation or the motivations for research neutron        sources;    -   One accelerator has the ability to produce many times the output        of a conventional power plant, which results in low cost per        unit of energy;    -   Favorable economics is obtained by capitalizing on this by using        the high-grade heat at high temperatures to produce hydrogen and        synthesize liquid fuels and lower the cost of other        energy-intensive industries such as steel and aluminum;    -   These economics apply to using the neutrons from the fusion        reactions to drive fission reactions in sub-critical fission        piles, and    -   Portions of the neutrons from the fusion and/or fission        reactions can be provided for research, production of isotopes        for applications in medicine and other purposes.

Current Amplification Processes Used to Generate Heavy Ion FusionIgnition Pulses

Accelerating heavy ions solved the problem of depositing the megaJoulesof beam energy in small targets containing fusion fuel. The beam energyalso must be delivered to the fuel targets in pulses with the shortdurations, e.g., of the order of 10 nanoseconds, consistent with thetimescale of igniting small fusion explosions by rapidly compressing andheating to ignition so that fusion burn is effected before thecompressed and heated fuel is able to fly apart. Using processesverifiable by the same analytical tools at the root of the design of allsuccessful accelerators, Martin, Maschke, and others defined examples ofsystems to reconfigure the beams and deliver them to the target on thistime scale.

The physics of particle beams employs mathematical methods thatcharacterize the motion of the particles that make up a beam, “acollection of particles confined in space”, in the terms of statisticalphysics. Pertinent to the present matter is the concept of beamemittance, a property that is conserved and thus a “constant of themotion”, reference being to the progress of the beam through theaccelerator and beam transport system. The emittance of a beamdetermines the diameter of the focal spot, to the 0^(th) order, i.e.,before accounting for such spot-size increasing effects as aberrations.By the statistical physics, the physical beams obey theorems holdingthat the emittance of a beam of identical particles cannot be decreasedby any conservative, i.e., reversible, operation on them throughexternal forces. That is, the emittance when a beam is born is the best(lowest) it can be. The emittance can and does grow in real machines,the design of which takes care to minimize the causes of suchdeleterious effects.

In slightly more general terms, the 6-dimensional phase space of a beamis conserved. The six dimensions are the positions of the particles inthe three conventional physical dimensions and the particles' relativemomentum components. Planes are defined in the phase space with theposition and momentum components for coordinates, with time used in theplace of the position coordinate in the direction of the beam's motion.The area occupied by the beam particles in each of these planes is thebeam's emittance in that plane.

The physics teaches that the sums of the emittances in the three planesremains constant, under the action of purely conservative externalforces, and some of the area of the emittance in one plane may be tradedto one of the others, or shared with both.

“Ballistic” focusing of charged particle beams is analogous to focusingbeams of light: the spot size depends on the emittance, of theparticle's paths coming into the electromagnetic lens, aberrations frombeam parameters (such as the momentum spread) inherent in the idealoptics, and imperfections in the magnetic fields of the lens. Forexample, the effect of focusing a particle beam that has a range ofmomentum per particle is similar to the “chromatic” aberration offocusing light with a variety of wavelengths (or photon energies, or“colors”), shown visibly in the spectrum from a prism, and the termchromatic aberration also is used in “particle beam optics”.

The term “brightness” characterizes the intensity of the number of beamparticles contained in the beam's 6-dimensional phase space. As thephase space volume occupied by the beam particles cannot shrink, thebeam brightness cannot be increased by conservative forces, during the“motion”. The brightness can and does decrease in real machines as aresult of any loss of beam particles in addition to distortions of thebeam that increase its effective emittance.

Ignition of inertially confined fusion reactions requires a beam that isextremely powerful, contains a substantial quantity of kinetic energy tobe deposited in the target to generate the high pressure required todrive the fuel to densities a hundred times the fuel's normal soliddensity. The ability to provide the unimprovable beam brightness at thesource and preserve enough of it during subsequent acceleration and beammanipulations to meet the demands of compressing the fuel (a.k.a.implosion) is the bedrock of heavy ion fusion driver technology.

The goal of the design of HIF drivers is to manipulate the beams so thatthe relatively low beam current at beam inception, at the source, whichis limited by the electro-magneto dynamics of the particles whose likeelectrical charge creates mutually repulsion forces tending to enlargethe beam in physical space. Expert evaluation of the first HIF systemconcepts to be proposed confirmed the judgment that HIF driver systemscould be built and operated to deposit energy in the required targetvolume and mass and in the short allowable time to achieve ignition.

This judgment, however, assumed an adequate concentration of experteffort would be applied to arrive at designs that would accomplish themission. Resources adequate for this effort have not be provided, andthe most vital HIF efforts continue the struggle via dual-purposeapplication of resources provided to continue the advance of particleaccelerator systems for research. This has placed the development of thecapable HIF drivers at risk of overlooking machine design approachesthat necessitate concentration on only beams comprised of heavy ions ina low charge state (lightly ionized), preferably with q=1, where q isthe number of electrons removed from the neutral atoms. This kind ofconcentration has yielded the novel features of the single pass RFdriver concept.

A review of the existing state of the art will preface description ofthe SPRFD's new features. A shorthand means to summarize the net effectof the several individual current amplification processes proposedduring the intense vetting of HIF “point” designs in 1975-80, was thefollowing equation:

I _(target) =I _(source) ×N _(sources) ×N _(injection) ×N _(compression)×N _(beams) _(_) _(on) _(_) _(target).   (1)

The total beam power on the target is the product of the total currentof particles (the same as the electric current for q=1, etc.) and thekinetic energy per particle. Ignitor pulse power of ca. 1 PW (1 petaWattis 1 billion megaWatts) is needed for ignition. This can be provided,for example, by some number of beams of 20 GeV ions with an aggregatecurrent of 50 kA (kiloAmperes). Early HIF driver concepts usingmainstream RF accelerator technology were judged capable of meeting therequirements promulgated by leading implosion experts. A problematicfactor related to the use of storage rings (which contribute the factorN_(injection) in Equation 1.) is described below. This problematicsituation is resolved in the SPRFD by the absence of storage rings, alsoas described below.

Another means of amplifying the eventual current (introduced in 1978 byBurke) accelerates ions of multiple isotopes. This method effectivelymultiplies the 6-dimensional phase space available to the designer,since each isotope is a different particle species, and thus not subjectto the constraint of Liouville's theorem. The advantageous effect ofmultiple isotopes is that a given set of parameters for energydeposition in the fusion target can be accomplished with 1. a set ofbeams that are each comprised of a different isotope (which aredifferent species (kinds) of particles whether these are isotopes of thesame atomic element, e.g., xenon, or different atomic elements, e.g.,xenon and lead), to allow each isotopic beam to have lower brightnessthan would be required if the energy deposition requirements were to bemet by a number (the factor N_(beams) in Equation 1.) of beams allcomprised of the same particle species. The motivation for the multipleisotope technique was to gain design margin by raising the capabilitiesof the beam, to drive implosion of fusion fuel “pellets”, beyond themarginal implosion abilities that were the targets of the early designs.In the arena of the energy supply industry where capital costs arelarge, reducing risks of unacceptable performance is mandatory at theconceptual level. The power of multiple beams may be regarded asrelieving pressure on other techniques for beamamplification/compression/compaction. However, the potential ways to usethis additional design factor to best advantage were not aggressivelyexplored, and only formally adopted in the internationally vetted“point” design called Heavy Ion Driven Inertial Fusion (HIDIF) in1995-97.

The means of compacting beams that have been devised to meet theignition requirements for inertial confinement fusion also may be usedsingly or in various combinations to increase the intensity of ion beamsfor beneficial applications.

Power production using only fusion reactions can be shown to be the mostdesirable of any baseload energy source, using inclusive metricsincluding abundance, safety, environmental impact, and cost. It iswidely recognized, however, that a shortfall in fusion energy producedfrom a given amount of energy used to drive the reactions may becompensated by causing the neutrons produced in the fusion reactions toinduce fission reactions in a suitable mass of fissionable fuel. Thisconstruct is called the fusion-fission hybrid. This construct haspotential advantages including the safety aspect in that the fissionpile would be sub-critical, since the need to emit slightly more thanone neutron per fission reaction is not needed. This feature plus thehigh energy of the fusion neutrons and their high fluxes enables thisconstruct to be devised to destroy high level radioactive waste in theprocess of generating power. If desired, in a limiting case of thisapplication, a HIF hybrid system could be totally dedicated todestroying radioactive waste.

To use neutrons from fusion reactions for applications such as researchand production of special isotopes, beams of neutrons in collimationchannels provided for the purpose may be directed into moderators toachieve the neutron spectra desired for these applications. The beamsalso may be directed into a neutron multiplying material or asub-critical mass of fission material to: 1. Increase the total numberof neutrons available that that point for the intended applications, 2.Exchange lower energy neutrons for the high energy fusion neutrons, and3. Be integrated with the moderator as previously said.

SUMMARY

A single-pass heavy-ion fusion system for power production from fusionreactions alone, power production that uses additional energy of fissionreactions obtained by driving a sub-critical fission pile with theneutrons from fusion reactions, destroying high-level and/or long-livedradioactive waste by intense bombardment with fusion neutrons, or forthe production of neutron beams for various applications includes a newarrangement of current multiplying processes that employs a multiplicityof isotopes to achieve the desired effect of distributing the task ofamplifying the current among all the various processes, to relievestress on any one process, and to increase the design margin for assuredICF (inertial confinement fusion) ignition for applications includingbut not restricted to the above list. The energy content and power ofthe ignition-driver pulses are greatly increased, thus increasingintensity of target heating and rendering reliable ignition readilyattainable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides a diagram of a single-pass HIF driver and a HIF systemfor power production and/or neutron source applications;

FIG. 2 provides an illustration of a chamber and protection of thechamber from neutrons by lithium sabots and liquid lithium sprays;

FIG. 3 provides an Illustration of a lithium sabot configured to causeexpansion in preferred directions, such as along the axis of acylindrical containment vessel;

FIG. 4 illustrates protection of a spherical reaction chamber fromneutrons by lithium streams;

FIG. 5 provides an illustration of a reaction chamber environment at anearly stage of lithium plasma expansion approximately one millisecondafter the fusion energy release;

FIG. 6 shows a schematic arrangement for an energy conversion toelectricity by a non-contacting, topping-cycle:

FIG. 7 provides a diagram of Pulsed direct energy conversion involvingtransmission, handling, and processing technology for timescales ofapproximately 10 microseconds;

FIG. 8 shows a reaction chamber with lithium restored to receive afusion energy release, with vacuum restored to allow propagation of aheavy-ion ignitor pulse;

FIG. 9 provides an illustration of a cylindrical containment vessel andprimary ancillary elements, principally primary heat exchangers, fuelinjector, and vacuum pumping for exhaust of reaction products and thefraction of the fuel that remains unreacted;

FIG. 10 provides a block diagram of a Heavy-ion Driver;

FIG. 11 provides a diagram of source, HVDC, and beam structure;

FIG. 12 provides a diagram of pulse structure from isotopic sources andan HVDC preaccelerator;

FIG. 13 provides a diagram of pulse structure in an RF accelerator FIG.14 illustrates a current amplification method by funneling microbunches;

FIG. 15 provides an Illustration of beam temporal structure in a sectionof the linear accelerator that includes interleaving microbunches at afrequency doubling;

FIG. 16 provides a diagram of an RF beam wobbler

FIG. 17 provides a diagram of a cylindrical target;

FIG. 18 provides a diagram illustrating target irradiation by a rotatingion beam;

FIG. 19 provides a diagram depicting fast ignition using heavy ions;

FIG. 20 provides a diagram illustrating heating of cylinder end capswith shorter-range ions to counteract internal pressure;

FIG. 21 provides a diagram illustrating cylinder end cap implosion;

FIG. 22 provides a diagram illustrating burn-though by shorter-rangeions;

FIG. 23 provides a diagram illustrating microbunches differentiallyaccelerated by offset RF frequency;

FIG. 24 provides a diagram illustrating snugging and snug-stopping;

FIG. 25 provides a diagram illustrating differential acceleration byoffset RF frequency;

FIG. 26 provides an illustration of increasing gap between slugs bysnugging;

FIG. 27 illustrates lengths and spacings of slugs using three speciesfor illustration;

FIG. 28 provides an illustration of a helical delay line;

FIG. 29 provides a diagram of microbunch motion downstream from aslicker;

FIG. 30 provides an illustration of potential minimum slug duration byslicking;

FIG. 31 provides an illustration of slicking that indicates relativecontributions to the overall momentum spread from microbunch phase spaceand slick kicks;

FIG. 32 provides an illustration showing the extensive thinning of thelongitudinal phase space ellipses that results in an optimal slickeffect; and

FIG. 33 provides an illustration of the last sections of the beam line,which shows: a. Culmination of the telescoping of multiple isotopicspecies slugs, b. Culmination of the slicking of microbunches withinslugs, and c. The ample timescales at the wobbler to allow modulation ofthe wobbler RF fields to realize: i. Beneficial target illuminationsymmetries and patterns, and ii. Adequate RF field rise time compared toa time gap between slugs having a large difference in speed.

DETAILED DESCRIPTION

A single-pass heavy-ion fusion system for power production from fusionreactions alone, power production that uses additional energy of fissionreactions obtained by driving a sub-critical fission pile with theneutrons from fusion reactions, destroying high-level and/or long-livedradioactive waste by intense bombardment with fusion neutrons, or forthe production of neutron beams for various applications includes a newarrangement of current multiplying processes that employs a multiplicityof isotopes to achieve the desired effect of distributing the task ofamplifying the current among all the various processes, to relievestress on any one process, and to increase the design margin for assuredICF (inertial confinement fusion) ignition for applications includingbut not restricted to the above list. The energy content and power ofthe ignition-driver pulses are greatly increased, thus increasingintensity of target heating and rendering reliable ignition readilyattainable. The present design does not use storage rings, thuseliminating issues that previously were judged by the community ofexperts to be problematic. Elimination of storage rings in turneliminates the emittance growth that attends multi-turn injection of thebeam into a storage ring. This results in the beam emittance being 1/10or less at the fusion target than beams in HIF driver configurationsthat use storage rings. This new low emittance makes it feasible tofocus the beam to a beam spot-on-target radius of ca. 50 μm, which inturn makes the concept of “fast ignition” feasible, and gains thepowerful advantages of fast ignition for high-gain from fusion pelletignition. Further innovations are to give the Heavy-ion Driverflexibility to drive multiple chambers in the most general case ofdifferent total distances between the linac output and each of thevarious chambers. Using multiple chambers steeply decreases the pro-ratacapital investment and operating costs per power production unit, inturn decreasing the cost of power or neutrons to users. The innovativemeans to increase the peak beam current also may be used singly or invarious combinations for applications where beam current higher thanotherwise obtainable is desired.

Lexicon of Novel and Key Terms

New terms are coined where indicated to facilitate description byremoving the ambiguity that is unavoidable as a result of using existingterms for new purposes. In particular, “beam compression”, “beamcompaction”, and the like apply to the whole beam generation process andto each of the steps that contributes to the process. Where newterminology is used, the convention will be to capitalize the terms. Inaddition to the novel terminology, the following lexicon includes someconventional terms to clarify possibly subtle meanings and as aconvenience for the reader.

Beamline: A beamline comprises an arrangement of magnets that guide thebeam down a vacuum tube, tube included. Several supporting things areimplicit: instruments to measure the beam properties without degradingthem; vacuum pumping; power supplies; associated controls; etc.

LEBT: This stands for sections of beamline for low energy beamtransport. The HIF (heavy ion fusion) Power project predicatesindustrialization in which operating ranges are tightly fit arounddesign nominal values, in contrast to maintaining the flexibility ofmulti-purpose research accelerators, which employ tunable low energytransport to match the beamline's transmission properties to beams of avariety of different beams, using source technology that is periodicallychanged to support evolution of the research mission, etc. HIF powerperforms the task of transporting the beams at low energy, butintegrates the acceleration stages for compactness, improved reliabilitythrough fewer parts, and some cost avoidance.

Master timing: Two parts: 1. An absolute time reference to coordinateDriver functions with Fusion Power Chamber functions and 2. Top-levelcoordination of Driver functions internally. Master Timing 1 isinitiated by signaling from the fuel injection system, because theaccelerator response time is on a much finer scale than that for theschedule of way-points for fuel injection. Master Timing 2 iscoordinated by harmonic relationships between the individual RF systemsthat perform individual functions in the beam generation process.

Compression or Compaction (relating to beam): In common with all ICFdrivers, the goal of the processes used to generate ignition pulses isto concentrate/compress/compact MJs of “wallplug” energy in the driver'sdelivery vehicle to be deposited in cubic millimeters of target materialin nanoseconds.

Compression (relating to fusion fuel): The definition of compression isthe ratio of the fuel density at the onset of fusion to the fuel densitybefore compression. Compression is a critical challenge for drivertechnologies, and classified for decades. Compression is key to thecriterion of propagating burn, which is the means to achieve a highratio of energy out to energy in. The primary mechanism for propagatingburn is re-deposition of the energy carried by the helium nuclei that isone product of D-T fusion. This gives the range of the helium nuclei inthe fuel around its point of origination as a key parameter for theonset of propagating burn. Stopping the helium ions and comprehensivetheoretical and simulation treatments, plus weapons technology and ICFresearch have established a parameter involving the characteristicdimension of the heated zone and the density of the fuel within thatzone.

Density×Length=rho·R=0.2-0.5 gm/cm{circumflex over ( )}2

The length parameter decreases as density increases. For sphericalgeometry (similar for cylindrical), the mass that must first be heatedto ignition if propagating burn is to start is:

Mass=Volume×Density=(4/3)πR{circumflex over ( )}3·rho

The parameter has key implications, most centrally the required degreeof fuel compression.

In terms of the propagating burn parameter, the mass is:

R{circumflex over ( )}3·rho=(rho·R){circumflex over ( )}3/rho{circumflexover ( )}2

Thus,

Mass=Constant·rho{circumflex over ( )}2.

In terms of the characteristic dimension, of interest relative totechnological capabilities for expediting propagating burn:

R{circumflex over ( )}3·rho=R{circumflex over ( )}2·(rho*R)

Thus,

Mass=Constant/R{circumflex over ( )}2.

The energy that must be deposited to raise the burning fuel is ˜kT timesthe number of particles in the plasma fuel, in standard fashion. Toreduce the amount of fuel that must be ignited, to bootstrap surroundingfuel into propagating burn, increasing the density is the mechanism.

From these relationships, a critical advantage accrues for heavy ions toaccomplish Fast Ignition with Telescoping Beams. For instance, theIsotopic Species for the Fast Ignition Pulse may be selected to heat atailored mass of pre-compressed fuel.

Microbunch: The beam in a radio-frequency accelerator is composed ofpackets of beam particles (ions, electrons, or other charged particles).Each RF cycle of the accelerator provides the same acceleration to eachmicrobunch. The present term is used interchangeably herein with theterm “micropulse”.

Macropulse: A train of microbunches.

Isotope, Isotopic Species: Ions that have identical nuclei.

Ion Species: An Isotopic Species that may be identified further by thecharge state of the ions.

Ion Source Hotel: An integrated cluster of ion sources including one foreach Species, and for the Species of both the Compression Pulse and theFast Ignition Pulse (if employed).

HVDC preaccelerator: Acceleration to high energy is by RF processes.Before RF processes can be applied, however, the speed of the beam mustbe raised to a value that corresponds to the synchronous speed requiredfor a practical RF accelerator structure. Critical characteristics thatare imprinted on the beam at its origin are strongly dependent on thevoltage of the preaccelerator.

Marquee RF Linac: The Marquee Linac facilitates acceleration of thespace-charge dominated low velocity beam by omitting bending of thebeams at the lowest velocity where beamline magnetic guidance andfocusing fields are least effective. The Marquee linac structure has anarray of parallel bore tubes. Each tube in the Marquee carries only oneIsotopic Species of beam. The bore tube array of the Marquee Linacmatches the bore hole pattern of the Source Hotel and the acceleratingcolumn in the HVDC preaccelerator. The beams of specified IsotopicSpecies in the array of bore tubes move in a programmed temporalsequence. The beams in temporal sequence that are in parallel beam tubesin the Marquee are fed into a single beam tube (one per Marquee) forfollowing beam pulse generation processes.

Telescoping: A process that accelerates a variety of different isotopesin individual macropulses in a sequence timed to cause the variousisotopic macropulses to telescope into each other in order to arrive atthe fusion target simultaneously or with a programmed sequence ofarrival times that achieves a desired ignition pulse power profile.Beams of different Isotopic Species propagate in a common beamline, withstatic magnetic steering and focusing, as a result of acceleratingdifferent Isotopic Species to correspondingly different energies suchthat all isotopes have the same magnetic rigidity, a function of ionmass, speed, and charge state. Telescoping at the fuel target is thepayoff for accelerating a multiplicity of Isotopic Species, whichmultiplies the six-dimensional phase space available to the designer.

Telescoper: The last section of the linear accelerator has provisions toemit different Isotopic Species with a common magnetic rigidity. Thiscauses the Slugs of various Isotopic Species with different masses tohave the different speeds as needed to arrive at the fusion target aspecified sequence. The control program for the Telescoper's RF waveformadjusts the time gaps between Slugs in each Ignition Pulse so that thevarious Slugs arrive according to a specified schedule at the fusionfuel targets in Multiple Chambers at various distances from theTelescoper.

Merging: Multiplying the current in a single beam by directingsimultaneous, parallel beams into a common magnetic beamline with anattendant increase in transverse emittance.

Slug: A macropulse of one of the isotopic species designed fortelescoping beams. A Slug is formally identical to a Macropulse. Theterm “Slug” or “Slug Species” or “Slug Macropulse” is used to avoidconfusion.

SubSlug: A Slug may comprise a small number (e.g., four) of identicalparts called SubSlugs. The SubSlug structure may be created by a gatingelectrode on the ion source, a “beam chopper” in the early portions ofthe accelerator, or a combination of both. The SubSlug structure sets upthe current amplification steps of Merging and Loop Stacking.

SlugTrain: A complete series of Isotopic Slugs. An ignition pulse maycomprise more than one Slug Train, to enable heating a fusion targetwith beams coming at the target from more than one direction. TheIsotopic Species and the Microbunches in the Slugs of different SlugTrains are identical, but the sequence of spaces between Slugs indifferent Slug Trains may be different, if needed to accommodatedifferent total beamline lengths to the fusion targets.

Loop Stacking: Uses a 360 degree bend in the beamline to return aSubSlug to the start of the Loop parallel to the input beamline insynchronicity with the next following SubSlug. The result of LoopStacking is to multiply the number of beamlines (e.g., one-Loop Stackingdoubles the number of beam lines) in a once-through process, in contrastto multi-turn injection in storage rings that stacks beams in transversephase space in a storage ring's single boretube.

Snug: The process of moving the individual Microbunches within each Slugcloser together.

Cradling: A feature programmed into an RF waveform involving a dynamicfrequency shifting, in particular the dynamic frequency shifting usedfor Snugging. The purpose of the feature is to maximize the efficiencyof the Snugger by making it possible to use the widest swing of phasesaround the zero crossing.

Snugger: The accelerator section that effects the Snugging process.

Bunch rotator: Bunch rotation refers to the orientation of the phasespace ellipse. The means to rotate the bunch in this sense is to work onthe bunch with electric fields that vary in time so that ions in thebunch that pass a point at different times receive differentaccelerations. The purpose of interest is to handle the conserved phasespace volume to retain the focusing to a spot while also manipulatingthe ions of the beam to arrive within the necessary pulse duration.

With the conventional definitions for the longitudinal phase space, thehorizontal axis represents time and the vertical axis representsmomentum. The phase space of a collection of particles (in this case,heavy ions) is “a constant of the motion”. In an RF accelerator, thephase space of the bunches evolves as in an elliptical shape that can besquished on one axis and will respond by stretching on the other axis.

If a bunch is tall and skinny, as shown in FIG. 26, it means themomentum spread is at a relatively large value and the time spread mustbe correspondingly at a relatively small value. Momentum spread resultsin chromatic aberrations, which must be within some limit (like 1%) ifthe bunch is focused to a small spot. If the momentum spread is toolarge, the chromatic aberrations may be the parameter that determinesspot size.

If a phase space ellipse is left alone to drift, the higher momentumparticles will move ahead and the lower momentum particles will fallbehind. The effect is that the ellipse will shear along the axis.

Bunch reflector: The purpose of reflection is to reset the phase spaceellipse so that it repeats the shear (described above) as the bunchlives and moves forward. One repeats the process, like Groundhog Day,until you get the bunch to where you want it to go.

Whereas “bunch rotation” connotes “laying the bunch down” on the timeaxis to minimize the momentum spread at the expense of time spread,bunch reflection rotates the bunch into its mirror image in either axis.Since it is not physical to reset the position of the bunch in time,physically, the reflection is done by shearing the bunch via the appliedelectric field—that means that the leading tip that is at the highestmomentum spread is sent down through the axis to an equally negativemomentum spread. Thus, the particle at the leading tip which has beenfastest becomes the slowest and begins falling toward the back, whilethe particle at the rear that was the slowest becomes the fastest andbegins moving toward the front.

For illustration, the HIDIF design rotates the bunch after it shears inphase space during a drift distance of 160 m. With the same parameters,a reflector would be needed every 320 m. It will be a bit easiertechnologically to reflect the bunches more frequently, as the HIDIFpushes the phase width of the bunch at the time when rotation is appliedto the extent that they have to fabricate a sawtooth waveform to knockthe ellipse down—i.e., to rotate it. They do that to get the longestlength along the time axis, and therefore the lowest momentum spread.What we want to accomplish can be done with much simpler demands on theRF waveshape.

Snug Stopper: The snugging process is stopped temporarily to allow themicrobunches to maintain their positions in the individual Slugs, whilethe Slugs “drift” to points at prescribed distances from the targets inmultiple reaction chambers.

Helical Delay Line (HDL) 2800: Shown in FIG. 28, a coiled length of beamline in an embodiment. All Slugs exit the Delay Line at approximatelythe same moment. The specific timing of the various Slugs is set to: a.allow time for a pulsed magnet to switch the slugs of different speciesa common beamline, in which the continue to the fusion target. Theschedule of arrival of the various Slugs (in each SlugTrain of anIgnition Pulse), set at the Ion Sources and coordinated with thewaveform of the RF power, results in Slugs arriving at their respectiveexit ports and, in turn, at the switch magnets to become realigned inthe SlugTrains in closer succession, with the spacing schedule set forTelescoping to culminate at the fusion fuel targets. The HDL carriesmultiple beams in parallel beamtubes, guided and focused by fields frommagnets that are integrated into a compact and economical array. Designof the beamlines, with switch magnets, at the exit port locationsaccommodates switching the Slug from each of the parallel beamlines intoa corresponding individual beamlines that continue the array of parallelbeamlines to the point where they are reinserted into beamlines thatcontinue to the Multiple Chambers with no further change to the numberof parallel beamlines.

Slicker: Restarts the Snugging process at a distance ahead of eachchamber such that the Microbunches will complete a specified slide overeach other to provide the desired current profile at the pellet. TheSlick process is subject to the constraints of the Liouville's Theorem.Simultaneous with progress of the Slicking process, individualmicrobunches stretch (or “shear”) while the area of the longitudinalphase space ellipse remains constant. The result is that individualmicrobunches become longer, skinnier ellipses in the longitudinal phasespace as they simultaneously approach the fusion target and slide on topof one another.

Fast Ignition: A class of fusion target designs that separates the twoprocesses of (a) fuel compression and (b) fuel ignition. Heavy ion beamdriver systems can be designed with or without the Fast Ignitionfeature. Fast Ignition improves the overall efficiency of achieving boththe fuel density and ignition temperature requirements.

Compression Pulse: The portion of the driver pulse that drives theprocesses that compress the fusion fuel.

Fast Ignition Pulse: The portion of the driver pulse that is focusedinto the approximate center of the precompressed fuel. The duration ofthe Fast Ignition pulse is characterized by the length of time for thefuel to disassemble, about the time for the fuel density to drop by afactor like two.

Ignition Pulse Profile: The series of arrival times of different Slugsat the fusion targets is set so as to form the temporal shape of thepulse at the target that most effectively “drives: a. the fuel into acompressed state, b. heats the fuel to ignition, or c. performs both aand b in an integrated process of compressing and heating.

Multiple Chambers: HIF fusion power is most economical if a single heavyion driver system ignites fusion pulses in a repeating sequence inmultiple fusion chambers. In the most general layouts of multi-chamberfusion power parks, the distance from the accelerator varies fromchamber to chamber. The dynamic beam generation processes mustaccommodate the variety of distances.

Final focusing lens: Final focusing means the focusing outside the wallof the chamber that then lets the beam fly ballistically to the target.The term ‘final’ distinguishes this from the many points where the beamis “focused” during transport (in “strong focusing” transport beamlines)to keep it from spreading.

FIG. 1 shows a diagram of a heavy-ion fusion system 1000, known hereinas an “Energy Park”, incorporating the innovations described hereinbelow. An Energy Park may use power production from fusion reactionsalone or by multiplying the fusion energy by using the fusion neutronsto drive fission reactions in sub-critical fission piles. As desired, anEnergy Park may incorporate features for destroying high levelradioactive waste by intensely bombarding such materials with fusionneutrons, or for the production of neutron beams for variousapplications. In brief, the system includes a plurality of reactionchambers 1002 in which pulses of heavy ions are directed to targets,generally known as pellets, containing fusion fuel. In the embodimentshown, the reaction chambers 1002 are grouped in a system 1001 known as“Industry Park”. As described herein below, the pulses occur in twophases: a compression pulse to pre-compress the fuel in the target inpreparation for a fast ignition pulse, which raises the temperature of arelatively small portion of the compressed fuel to ca. 10 keV to causevigorous fusion reactions. Some of the energy carried by the heliumnucleus emitted from the D-T fusion reaction is redeposited in the fuel,raising its temperature further and accelerating its reaction rate. Inthe process called “propagating burn”, fuel adjacent to the fast-ignitedmass is ignited by heat transferred from the fast-ignited fuel andsubsequently self-heated by redeposition of the energy of the heliumnucleus from the fusion reactions, photon flow, and hydrodynamicprocesses. The burn propagates very quickly throughout the fuel, causingca. 40% of the fuel to burn. The heavy-ion beams 1004, 1005 aretypically routed toward the reaction chamber along beamlines (also 1004,1005). In one embodiment, each of the reaction chambers 1002 is servicedby two beamlines, each beamline delivering four heavy-ion beams. Anaccelerator 1003 includes an ion source 1006, an accelerator section1007 and a current amplification module 1008, known herein as a“snugger”. Ions are emitted from the source 1006 and received by theaccelerator 1007, where, in addition to being accelerated, they undergoother processing such as focusing, until they are emitted from theaccelerator section and received by the snugger 1008. After beingemitted from the snugger, the ions undergo further processing, describedin detail herein below, before they are allowed to drift in thedirection of the industry park 1001, comprising the reaction chambers1002. Energy liberated as a result of fusion reactions is coupled to apower plant for conversion to other forms of energy. In applicationswhere the fusion energy output is amplified by fission reactions in asub-critical fission pile placed so as to be irradiated by neutrons fromthe fusion reactions and thereby to caused to undergo fission reactions,the net energy from fusion and fission processes is coupled to a powerplant for conversion to other forms of energy. This is similar to caseof only fusion energy, but with additional features appropriate forhandling fission materials.

To use neutrons from fusion reactions for applications such as researchand production of special isotopes, beams of neutrons in collimationchannels provided for the purpose may be directed into moderators toachieve the neutron spectra desired for these applications. The beamsalso may be directed into a neutron multiplying material or asub-critical mass of fission material to: 1. Increase the total numberof neutrons available that that point for the intended applications, 2.Exchange lower energy neutrons for the high energy fusion neutrons, and3. Be integrated with the moderator as previously said.

Clean Reaction Chamber Innovations

The Heavy-ion Driver delivers an Ignitor Pulse via a practical number ofbeams to the entrance ports into the Reaction Chamber (e.g., eight beamstotal, with four on each of two sides). The salient features of thechamber embody precautions taken to convert the 14 MeV neutron energy toheat without reaching the chamber 2000 walls. As shown in FIG. 2, thisis accomplished by initiating the reaction with the fuel pellet inside asubstantial body of lithium 2001. In the simplest example, this is asphere of lithium about 60 cm in diameter, hereinafter known as alithium sabot. Additional protection for the chamber 2000 is provided bylithium spray and droplets 2002.

The lithium sabots 3000 also shield the fuel targets at cryogenictemperatures from the elevated temperature in the reaction chamber. Thefuel-transporting sabots may be variously shaped and configured, withappropriate access holes 3001 for the heavy ion beams. In the embodimentof FIG. 3, the lithium sabot is spherical in shape, however otherembodiments exist wherein the sabot assumes other shapes, cylinders orcones, for example. In all cases the thickness of the lithium must be atleast 30 centimeters from pellet to the closest boundary of the pelletholder. Collisions between the neutrons and the lithium atoms over thisradius convert a preponderance of the kinetic energy carried by theneutrons to heat. Nuclear reactions of the neutrons with the lithiumregenerate tritium, produce additional helium and more heat, and resultin a preponderance of the neutrons being captured and denied access tothe materials of the chamber walls. As shown in FIG. 3, the lithiumsabot 3000 may be configured to cause expansion in preferred directions3002, such as along the axis of a cylindrical containment vessel.

The reaction chamber 2000 can have various shapes from spherical tocylindrical to composite shapes of various conic surfaces. FIG. 4illustrates an internal view 4000 of a reaction chamber 2000,schematically illustrating a rain of protective lithium droplets 4001,is shown. A bounding envelope must withstand both high vacuum andmoderate transient pressures and will be constructed from steel, andother materials. Leaching of alloy materials is avoided by materialscontacting only lithium returning from the low temperature end of theheat exchanger. Additional lifetime is added to the chamber by claddingof alloy steels with simple iron on the surfaces facing lithium. Lithiumflowing in conduits such as pipes and/or tubes also flows at, mainly,the low, incoming fluid temperature, approximately the melting point oflithium (180.5° C.).

The heated lithium cools from a plasma state and eventually condenses ina series of phases, and the chamber is back to its ‘cool’ state readyfor another reaction to take place in a fraction of a second. Thisrequires pumping tons of lithium per pulse to cool and protect thechamber walls, e.g., approximately five tons for fusion releases of twoBOE (barrel of oil equivalents) each, or 50 tons for twenty BOEreleases. The heated lithium goes through the heat exchangers andreturns as cool fluid to cool the chamber and re-establish the vacuum(low gas density) necessary for the ignitor beam to propagate across thechamber radius to ignite the next fuel target.

The total mass of lithium for each fusion pulse, injected into thechamber at flow rates tailored along the chamber's length for thedesired temperature history, is sized according to the integrated schemeof fuel sabot injection, ignitor beam passage, fusion energy containmentand conversion, expansion of the lithium, extinguishing the plasma,further cooling to heat transfer temperatures, and restoring therequired pre-pulse environment. These phases compare to the processes ofan internal combustion engine operating on chemical combustion:

-   -   power stroke with power take off;    -   exhaust of spent fuel charge;    -   rejection of unused heat;    -   fuel charge injection; and    -   ignition.

FIG. 5 provides an illustration of a Chamber 5000 environment at anearly stage of lithium plasma expansion around one microsecond after thefusion energy release. For illustration, fusion releases equivalent tothe energy contained in two barrels of oil, absorbed in the lithiumsabot, form electrically conducting lithium plasmas. Regarding theplasma as the thermodynamic working fluid at this stage, non-contactingmeans may be provided that operate with this extremely high temperatureworking fluid, to realize a topping cycle with a revolutionary increasein conversion efficiency. The novelty in the present embodiment of thisenergy conversion technique is that it applies to the combined heat ofthe electrically neutral neutron, which carries 80% of the total fusionenergy release, as well as the electrically charged helium nucleus,which carries only 20% of the total fusion energy release. FIG. 6 showsa schematic arrangement 6000 for a energy conversion directly toelectricity by a non-contacting, topping-cycle. As shown in the diagram7000 of FIG. 7, pulsed direct conversion involves transmission,handling, and processing technology for timescales of around 10microseconds.

Neutrons are insulated from the chamber walls by flows and sprays of lowtemperature lithium returned from the heat exchanger 9001. A largechamber for producing 100 BOE, or more, per minute provides adequate gasdynamic expansion. The volume of the plasma that forms upon ignition ofthe fuel pellet at the center of the Lithium may be about 1440 cubicmeters. Microseconds after the pellet undergoes Fusion the lithiumsurrounding the fuel pellet has vaporized to become Plasma whose energyis being harvested by direct conversion to electromagnetic fields andelectric currents.

Further cooling and chamber wall protection is accomplished by fillingthe chamber volume with sprays of liquid lithium droplets. Out to acertain distance from the fusion burn, this lithium becomes part of theplasma. Further out, lithium is even vaporized. Lithium covering thewalls protects the walls by ablation, and the lithium beneath theablation boundary maintains the walls at the modest temperature of thelithium returned from the heat exchanger 3001 subsystem. Heat is notextracted through the main walls of the chamber, as the bulk of the heatflows towards the ends of the cylindrical expansion volume. The lithiumworking fluid progressively cools by interaction with lithium spraysalong the axis of the cylindrical chamber, and condenses beyond thedirect conversion zone. Condensed, hot lithium comes in contact with theprimary heat exchanger 3001 and heat is transferred to a secondary fluidfor use in processes located outside the primary containment, defined asthe lithium boundary.

Exhaust of fusion reaction products concerns primarily the helium andtritium produced. Tritium is needed to fuel later D-T(deuterium-tritium) pulses. Tritium containment also is the chiefradiological hazard of the entire HIF power system. The large body ofknowledge regarding tritium safety is clear on the engineeringrequirements. The HIF chamber system economically accommodates severallayers of redundant features to assure tritium safety.

Prior to the next energy release, the low temperature lithium acts as agetter pump to scavenge lithium vapor left behind by the power andexhaust dynamics.

FIG. 8 shows a Chamber 8000 with lithium restored to receive a fusionenergy release, with vacuum restored to allow propagation of the HIFignitor pulse.

The temperature of the lithium progressively decreases as it functionsto:

-   -   capture a preponderant fraction of the neutrons and essentially        100% of their energy;    -   to knock down the pressures of the explosive pulse; and    -   to convert energy to electricity in non-contacting,        direct-conversion processes. Lithium in liquid form at different        positions in the reaction chamber experiences temperatures as        low as 200 degrees Celsius to temperatures as high as 1200        degrees Celsius each time a pellet ignites, not counting the        room temperature lithium of the fuel sabot or the temperatures        of this and immediately surrounding lithium during the plasma        state. This heat flux, along with the electrical energy        extracted by direct conversion, is the major product of the        fusion reaction. Secondary heat exchangers convert this heat to        other products such as hydrogen gas for use in producing        synthetic fuels, steam for use in conventional steam turbines,        and heat for the desalinization of water by evaporation.

An external view 9000 of a cylindrical reaction chamber 9001 and itsprimary heat exchange system 9002 is shown in FIG. 9. In addition, afuel injector, and vacuum pumping for exhaust of reaction products andthe fraction of the fuel that remains unreacted (typically about half).

Because tritium is released to the working fluid during the reaction itmust be recovered to meet governmental radiation safety standards and toprovide the Tritium necessary for subsequent reactions. To assure thatno Tritium is accidentally released to the environment, the whole of thereaction vessel and its heat exchangers is typically enclosed in asecondary containment vessel. This vessel may be filled with a gas thatis not reactive with Lithium, for example Argon.

Supporting activities for the reaction vessel 2000 include:

-   -   Lithium pumps;    -   Pellet making facilities;    -   Lithium sphere, or other carrier, manufacturing facilities;    -   Tritium recovery facilities;    -   Large vacuum pumps; and    -   Secondary heat exchangers.

Of all of these supporting activities, only the secondary heatexchangers can be outside the secondary containment structure. Allfunctions internal to the secondary containment are capable of operatingremotely, for no oxygen or water or water vapor can be located where itcould come in contact with the lithium. Lithium oxidizes rapidly in thepresence of air and reacts violently when in contact with water.

Ignitor Pulse Structure and Timing

It is instructive to regard the Driver design from the vantage point ofthe controls system. This especially aids design illumination byproviding a common framework to describe the manner in which theindividual processes function and the requirements to coordinate them.Referring now to FIG. 10, a top-level functional block diagram of an HIFDriver 1000 is shown:

-   -   Front end 1001;        -   isotopic ion sources (d, e) 1002; timing source;        -   HVDC (d, e) 1003;        -   RF capture and initial acceleration (d,e) 1004; beam            synching to fractional RF period begins; continues to            Slicker RF;    -   Isotope alignment (d, e) 1005;    -   Acceleration and Zip compaction (z) 1006;    -   Snug compaction 1007;    -   Isotope differential acceleration begins telescope compaction        1008;        -   RF bunch maintenance begins;    -   Merge compaction 1009;    -   Slug-slug delay-line compaction 1010;    -   Isotope-isotope delay-line compaction 1011;    -   Isotope-isotope telescoping drift compaction 1012;        -   Switch into beamline into specific chamber 1020;    -   Slick kick starts slick compaction 1013;        -   RF bunch maintenance ends 1021;    -   Wobbler starts beam hollow (g) 1014;    -   Focus lens (g) 1015;    -   Beam neutralization 1016;    -   Fuel pellet 1017; and    -   Timing target 1018.

The above design provides the timing accuracy to cause the variousdynamic processes of beam generation to culminate at fusion fuel targetswith including power profile and aiming, at fusion targets power profileand to meet the targets as they move through the target zone. The designalso provides the timing flexibility required to achieve specifiedIgnitor Pulse parameters, in Multiple Chambers. Overall Ignitor Pulseprogramming is able to vary the spacing of Isotopes based first on thespeeds of the different ions a table of Isotopic Species. The timing forsource gating is derived from the master clock of the RF synchronizer.

Improvements in the areas of each of the functional blocks include:

New Features of Ion Sources and Low Velocity Acceleration:

Most of the new mechanisms for the compaction of the beam come after thebeam leaves the linac. The new design also involves changes in featuresof the linac, which complement the improved beam reconfiguration(manipulation) design. Most novel are the features related to the moreeffective use of a larger number of different Isotopic Species than inprevious HIF driver designs. The Front Ends of the accelerator include acombination of underused but previously demonstrated features plus thenovel integration of the first RFQ (radiofrequency quadrupole linacsection).

Ion Source Hotel

The Ion Source Hotel (array) integrates many isotopic sources into acompact cluster of one for each Species, including both the Species forthe Compression Pulse and for the Fast Ignition Pulse (if employed). Theoutput pulses from individual isotopic sources are given synchronizedtiming via: 1. a gate voltage and 2. pulsed excitation of the ionemission process in a programmed series to produce the basic buildingblock of Slug beam lets in the desired sequence. The compact array ofbeams enables the HVDC column to continue the parallel geometry of thebeam paths from the specified array of apertures.

HVDC Preaccelerator

HVDC source technology in excess of 1 MV, e.g., 1.5 MV demonstrated inprior art, viz., Argonne National Laboratory 1976-80. In conventionaldesign practice, the peak current limit for transport in a strongfocusing magnetic beamline increases with (βy)^(5/3) (β=v/c, c=speed oflight, γ=relativistic factor). Using commercial ion source technologyand commercial HVDC sources, this scaling contributes an importantfactor to increasing the peak current of each beam, with the desired lowbeam emittance, at the output of the linear accelerator. The array ofbeams is suitably compact for immediate transfer (close-coupling), withcontinuation of spatial configuration of the array of apertures and beamcenterlines, to the following Marquee RF Linac.

Marquee RF Linac

The Marquee Linac facilitates acceleration of the space-chargedominated, low velocity beam by not significantly bending the beams atthe lowest velocities where magnetic focusing fields are less effective.The Marquee linac structure has an array of parallel beam channelsmatching the pattern of beam centerlines in the Source Hotel and theaccelerating column in the HVDC preaccelerator. Each beam channel in theMarquee carries only one Isotopic Species of beam. The pulsed beams ofspecified Isotopic Species (aka Isotopic Macropulses or Sluggettes)occur in the array of beam channels in the programmed temporal sequenceimprinted at the ion sources.

The first section of the Marquee Linac is a radiofrequency quadupole(RFQ) accelerator structure. The ion speed at the output of the Marqueewill be specified in detailed design based on the beam physics andcapabilities of the beam handling component technology (e.g., pulsedmagnets). In one embodiment, the RF Marquee section may comprise onlyRFQ tanks at the one RF frequency (i.e., no jump of RF frequency).

Aligner (Aka Marquee Collapser)

After the Marquee linac section, the beams that exit in temporalsequence from the parallel beam channels are fed into a single beamchannel, i.e., one channel downstream of each Marquee, by a beamlineswitchyard using moderately fast switch magnets. Specifying a practicalrise time of these magnetic switches will be a determinant of thetemporal gap between Slugs, along with the requirements for downstreambeam handling and the eventual telescoping of species. After the Aligner(Collapser), all isotopic Sluggettes, emitted from each one of themultiple front ends, are transported and further accelerated in one beamchannel.

Overview of Current Multiplication Processes Accelerator Driver Summary

Telescoping is exploited, e.g., 10 Isotopes for tenfold increase inworking volume of 6-dimensional phase space. State of the art sourcetechnology is used.A State of the art Preaccelerator HVDC of ˜1 MV is used, cf. ArgonneNational Laboratory 1976-80. A Linac emits multiple parallel beams,e.g., four.

Stacking in transverse phase space uses a low number, e.g., two in eachtransverse plane. Ignitor Pulses are generated with once-throughaccelerators and beamlines. Storage rings are not used. Microbunchstructure is maintained all the way to the fusion fuel target, i.e.,identity and integrity of each RF microbunch of ions is maintained.Macropulses of individual isotopes, called Slugs, contract (called Snug)due to differential acceleration in Snuggers, e.g., ±5% to ±10% of thenominal speed, using successive blocks of linear accelerator tanksoperating at progressively higher frequencies, e.g., from 400 Hz forfirst block and 4 GHz for the last block.

The last sections of the Snugger, called the Snug Stopper, reverse thesense of the input Snugging voltage to return the nominal speed of allmicrobunches to the nominal speed of the Isotopic Slug. The beam passesthrough a Helical Delay Line 2800 that removes space from between Slugcentroids by magnetically switching out successive Slugs from successivecoils of the Helix, at programmed times such that, when they arereinjected into common beamlines, they take the next programmed step ofpower amplification.

This set of beamlines, e.g., four beamlines, continues to switch pointsthat route the beams to one of the multiple fusion chambers. Thedifferential distance to multiple fusion chambers is accommodated by thecentral timing program for computer-controlled operation. To providetwo-sided target illumination, a set of two Slug Trains, each comprisinga Compression Pulse and a Fast Ignition Pulse, are produced in series bythe target for both Slug Trains. The accelerator may be timed such thatdrift distances and other parameters for Snugging and Telescopingsimultaneously achieve maximum intensity timed in coordination with fueltarget timing.

A low factor of emittance multiplication, e.g., 2.5×, realizes astep-change improvement for low emittance at the fusion fuel target. TheFast Ignition requirement of small spot diameter is enabled by thesmaller emittance. Chromatic aberrations are controlled within practicallimits by conservation of longitudinal phase space RF of the beamstructure at the microbunch level, e.g., 1% momentum spread in the finalfocus lens.

Overall RF-based coordination produces and delivers Ignitor Pulses tofusion targets on absolute, end-to-end timing to the accuracy of afraction of an RF period. Substantial timing errors are permissible, asthe limit of the capability exceeds foreseeable requirements.

Programmed timing of the pulsing of the array of ion sources, HVDC, andRF power provides the large flexibility (bandwidth) of the designconcept to dial-in the sequence of beam generation processes in thecomputer control program.

Ignitor Pulse Structure and Timing

It is instructive to regard the Driver design from the vantage point ofthe controls system. This especially aids design illumination byproviding a common framework to describe the manner in which theindividual processes function and the requirements to coordinate them.Referring now to FIG. 10, a top-level functional block diagram of HIFDriver 1000 is shown:

-   -   ion sources 1001;    -   preaccelerator HVDC (high voltage direct current) 1002;    -   an RF linear accelerator section 1003;    -   a current amplification section 1004; and    -   multiple reaction chambers 1005.

The above design provides the timing accuracy to cause the variousdynamic processes of beam generation to culminate at fusion fuel targetswith including power profile and aiming, at fusion targets power profileand to meet the targets as they move through the target zone. The designalso provides the timing flexibility required to achieve t specifiedIgnitor Pulse parameters, in Multiple Chambers. Overall Ignitor Pulseprogramming is able to vary the spacing of Isotopes based first on thespeeds of the different ions a table of Isotopic Species. The timing forsource gating is derived from the master clock of the RF synchronizer.

A beam diagnostics and accelerator controls system establishes accuracyof the arrival of the Ignitor Pulse to timescales for the IgnitorPulse's temporal waveform, e.g., nanoseconds to tenths of nanoseconds.Synchronization of the absolute arrival time of the Ignitor Pulse withthe passage of the fusion fuel target as it falls through the bullseyeis obtained by precise tracking of the fuel target's position andorientation by tracking means such as reticules affixed to the targetsand tracking observation by means, e.g., optical, that provide precisionmeasurements of the position, speed and rotation of each target withinits lithium sabot. Provision of such tracking means are facilitated bythe use of the sabot and the relatively large size of each sabot-targetassembly.

The Driver is computer operated, using centralized Master Timing via thecoordinating effect of synchronizing RF waveforms. Distributed timingcontrol provides realtime corrective responses, using for example theability (provided by the ionic speeds being less than control signalpropagation speeds) to feed-forward data about the beam position andother parameters. The state of the art for the precise timing andcontrol of RF fields extends to approximately one part in ten thousand.

Delivery of a high current short duration pulse to the fusion pellettarget located in each of many chambers at various distances from thesource is depends on the pulse structure of the ion source. The precisetiming of each beam to each chamber is unique and accounts for thedistance to the chamber for the specific beam, the properties of all ofthe switches and accelerators in the beam path, and the precise lengthsof each of the delay paths. It also may take into account thedifferences in mass of the individual isotopic species used in the ionbeam.

When the properties of the pulse at the target are defined by the energyrelease needs of the fuel pellet, the challenge is to amplify the sourceion current via the pulse structure and the accelerator properties tothe magnitude required by the ignition parameters at the target.

This amplification is dependent upon cascading a series of steps ofcurrent amplification as described in subsequent sections, but it is alldependent on the ion source current parameters and their precise timingstructure as they leave the sources. The timing within the pulsestructure 1102 that evolves as a result of the beam generation processesis set by the release of ions via grid gating at the source 1101. Theheaviest ions are released first and are followed sequentially by eachof the lighter species in descending isotopic mass order. One source foreach of the isotopes is integrated into a compact structure called aSource Hotel 1101, as shown in FIG. 11.

The ion source within a Source Hotel 1101 is gated to release identicalduration macropulses 1200, FIG. 12 as a set of equal parts, e.g., four,of the feature of the beam structure called an Isotopic Slug. TheIsotopic Slugs are sequential and do not overlap, propagating inparallel channels. The source beams are accelerated by HVDC inPreaccelerators, with one Source Hotel extractor integrated with theHVDC column electrodes in each Preaccelerator. The electrodes have apattern of apertures that matches those of the Hotel. For purposes ofillustration, the emission from sixty-four, state of the art SourceHotel-Preaccelerator assemblies comfortably exceeds the requirements ofthe most stringent Ignitor Pulse parameters.

The sequence of Isotope Slugs for the Fast Ignition (FI) pulse isemitted first (i.e., using heavier ions for the FI Pulse than for theCompression Pulse), with the first Slug containing the heaviest isotope.Next, the Slugs for the Compression Pulse are released after a pause intime determined by the velocity differences between the FI ions and thelengths of beamline determined by details of the series of beamgeneration processes. The timed release of each of the differentIsotopic Slugs follows in descending isotopic mass order, with aschedule of delays between Slugs that is determined by the ion mass(which determines its speed in a series of isotopes by the TelescopingCondition of equal magnetic rigidity), the accelerator length, and thelength of the beamline to a fusion target in a given reaction Chamber.

Each complete series of Isotopic Slugs forms a non-overlapping sequenceof Slugs called a Slug Train. The total release duration for each Slugfor the Compression Pulse (which many times the total energy as the FastIgnition Pulse) is nominally 10 μsec and the overall release time SlugTrain lies between 400 μsec and 500 μsec, depending upon the distance tothe most distant reaction chamber.

In the first RF accelerator section, the Slugs continue to beaccelerated as parallel beams with the Source Hotel's array. All theaccelerating channels are on, regardless of which channel a Slug is inat a given axial location and time. Visualized end-on, the emission ofSlugs from the individual channels is similar to a theatre Marquee withonly one light blinking at a time in a pattern with complex but specifictiming.

Immediately downstream from the Preaccelerator, each macropulse entersthe first section of the RF accelerator and is imprinted with themicropulse structure. The strength of the accelerating field over theentire linear accelerator is higher for Slugs with higher mass, toaccelerate the higher mass to an equal speed at each point along thelinac.

Referring now to FIG. 13, shown is a diagram 1300 of a pulse structurein the RF accelerator.

The first RF accelerator is a multi-channel radiofrequency quadupole, orRFQ, which integrates RF quadrupole electric focusing and acceleration.The RF field in the initial section of the RFQ provides strong focusingfields and a smoothly increasing accelerating field to approachisentropic conversion of the DC incoming Slug beam into microbunches(μbunches) in a continuous stream at the RF frequency. For illustration,each μbunch contains a number of ions of the order of ten billion. Anentire Ignition Pulse (e.g., carrying a total of 20 MJ of ions thatcarry 20 GeV (3.2 nanoJoules) each) contains about eighty thousand ofthese elemental, μbunch groups of the energy-carrying heavy ions. Thepurpose for continuing the Marquee in the first stage of RF accelerationis to delay bending the beam until the speed of the ions is able toefficiently use magnetic focusing to handle the space charge forcesassociated with high beam current. The initial speeds of the heavy ionsfor HIF Drivers (i.e., in the front end) are especially slow because, toachieve the brightest beam, the preferred choice is for the ions to besingly charged.

After the ion speed is raised in the RF accelerator section with theMarquee array of parallel Isotopic Slugs, the beam is fed to anaccelerator section operating at twice the frequency of the RF Marquee,e.g., 12.5 MHz. Between the two RF structures, the beams from theMarquee are Aligned for insertion into the 25 MHz structure as acollinear Slug Train. The array of the Aligner's magnetic beamlines,e.g., sixteen (nominally ten for the Compression Pulse and six for theFast Ignition Pulse), are routed, one each, to a corresponding series ofAC switch magnets (one on the Aligned beamline for each Slug) that bendthe Slugs into a common, Aligned magnetic transport channel, in a SlugTrain with the specified time structure. Prior art also describes analignment process that integrates the interleaving (or funneling) ofmicrobunches at the frequency doublings. Prior art further describes aprocess of interleaving two beams that smoothly integrates with thedesign of an RFQ accelerator. Using this concept, the Aligner alsodoubles the average current of a Slug. FIG. 14 provides a diagram 1400showing the interleaving of two beams of microbunches 1401, 1402 into asingle beam 1403 having twice the frequency of the original beams 1401,1402.

The beams emerge in the higher frequency RF structure downstreamoperating at 25 MHz (e.g., a second RFQ) with twice as many micropulsesin each Slug, and half the number of parallel beams. The beams continueinto the next structure and upon emergence are interleaved with anadjacent beam once again thus again doubling the number of micropulsesand halving the number of beams that need to enter the next linacsection. After each subsequent acceleration section the beams continueto have their micropulses doubled by interleaving until four beamsremain at the end of the 200 MHz accelerator.

With interleaving repeated at each of the frequency steps, e.g., five,the current of each Slug multiplies by a factor of thirty-two. FIG. 15provides a diagram 1500 illustrating the process of“funneling”-interleaving at frequency doublings. The timing structurefor the RF fields in any given section of the linear accelerator isillustrated in FIG. 15. The beam forming process is repeated a secondtime, producing two sequential Slug Trains. The two Slug Trains areseparated later, to deliver one beam to each side of the destinationreaction Chamber. For illustration, the result of interleaving is fourparallel beams in the last section of the linac used by the slower groupof Slugs, e.g., the substantially heavier ions used for the FastIgnition Pulse. The final portion of this linac section, called theTelescoper, has a pulsed switch magnet for each of the Slugs. Theswitches are located where the Slug in question reaches the specifiedCommon Beam Rigidity. Once that magnetic stiffness is reached, they areremoved from the accelerator and fed into a Telescoping beamline, i.e.,a magnetic beamline in which Slugs of the same stiffness but differentspeed are able to catch up to each other. The following (faster) Slugsfor the Fast Ignition Pulse are fed into an accelerator with twice thefrequency (e.g., 400 MHz), but are not interleaved, and continue as fourparallel beams of Slugs with RF-synchronized microbunch structures. Thefinal portion of this linac section is, again, a Telescoper, integratinga pulsed switch magnet (between linac tanks) for each of the at thepoint where the Slug in question reaches the specified Common BeamRigidity, which is identical with Rigidity of the ions in the group ofslower Slugs.

Once all slugs are out of the Telescoper, the four beam lines are mergedto form one beam line with four times the current. The radiofrequencymicrostructure of the merged beam is the same as for each of thepre-merged parallel beams, as is the SubSlug structure.

Next, alternating SubSlugs from the merged beam line are immediatelyswitched into the start of a new beamline, which is bent into 360 degreeloop, to arrive in RF synchronism with the next SubSlug. This LoopStacking will use a series of two loops (sending four parallel beamsdownstream), or one (sending two parallel beams downstream). The resultof Loop Stacking is to position multiple SubSlugs at precisely equaldistances from the fusion target.

Downstream, the Slugs are the length of a SubSlug, and the SubSlugtiming feature goes away. The number of parallel beams in parallelbeamlines at this point (i.e., either two or four, in this illustration)continues to the Chamber and the fusion target, with one of the twoSlugTrains magnetically switched into one or the other of two sets ofthe beamlines for two-sided target heating.

All operations beyond the Telescoper may take into account the fact thatthe Slugs are moving at different velocities relative to each other andthus are getting progressively closer together at the same time that theRF frequency of the Snugger is bringing the micropulse structure tohigher and higher frequency. The Snug Stopper freezes themicrostructure, but the Slugs continue to drift together until, at thetarget, they all arrive on their pre-programmed schedule.

Specified RF waveforms are generated at low power by a Master andSubordinate Arbitrary Waveform generators. The Driver's RF Master Clockcommunicates with the Chamber controls, in particular those concernedwith the dynamic injection of fuel charges in their protective sabots.

The total duration of beam emitted by the linear accelerator for eachignition pulse is, for example 200 μsec. Blank spaces in the overallbeam profile are needed for a number of purposes, including:

-   -   Gating the outputs of the ion sources for different Isotopes;    -   Subdividing Isotopic Slugs into a number (e.g., four) of        SubSlugs;    -   Switching alternating SubSlugs into parallel beamlines in Loop        Stacking;    -   Raising or lowering RF accelerating gradients between passage of        one Isotopic Slug and the next, to accelerate isotopes with        different masses to equal speeds at each point of the path        through the Fixed Beta-Profile linac and Telescoper;    -   Raising or lowering the RF frequency in the beam manipulation        processes of Snugging, Snug Stopping, and Slicking;    -   Switching Slugs after the HDL from individual beamlines into        common beamlines;    -   Bifurcating beams for RF bunch maintenance in the HDL and at the        Slicker.

Certain processes can exploit the same time gap as certain others. Thus,the required sum the time gaps may be less than the sum of the times ofthe gaps for processes individually. Prominent features of the designare specifically for the purpose of removing these gaps, includingTelescoping of Multiple Ion Species and by the action of the HelicalDelay Line 2800.

New and Modified Features and Processes for Ignitor Pulse Generation

The following list is in the approximate order in which the processesoccur during generation of an Ignitor Pulse:

1. From a closely-packed array of ion sources, generate a time-sequencedseries of separate beams of a specific set of ion species in individualparallel channels. The set of heavy ion species may comprise isotopes ofthe same atomic element or a combination of atomic elements.

2. Accelerate the multiple beams from the source array in a HVDCstructure with: the same array of parallel channels and close-coupled tothe ion sources to maximize beam brightness.

3. Capture the DC beam in the RF fields of a radiofrequency quadrupoleaccelerator (RFQ) which: 1. Is integrated with and close-coupled to theHVDC accelerating structure, 2. Converts the time-sequenced DC pulses ofthe isotopic beams in parallel channels into trains (called a“micropulses”) of “micropulses” at the RF frequency and 3. Furtheraccelerates the ions to facilitate beam transport using magnetic fields.

4. Use magnetic fields to direct the time-sequenced beams of differentisotopes onto a common beamline for further acceleration in the samesequence.

5. Double the current per isotopic beam macropulse by “zippering” themicropulses of previously separate beams of each isotopes into a singleline, at points where beams are transported from an acceleratorstructure at a given RF frequency to a structure at twice thatfrequency, as required to accommodate the progressively increasing speedof the ions.

6. Move microbunches within each Slug closer together (Snug). Theprocess is illustrated in FIG. 24. Microbunches within a Slug aredifferentially accelerated and decelerated, progressing from maximumdeceleration of the first microbunch in a Slug to maximum accelerationof the last microbunch in a Slug;

7. Differential microbunch acceleration is achieved by offsetting the RFfrequency of the Snugger linear accelerator sections. From the firstmicrobunch experiencing the most deceleration, the phase of the RF fieldexperienced by successive micropulses moves progressively higher on theRF waveform, until the last microbunch in a Slug experiences the mostdifferential acceleration;

8. The absolute frequency offset is calculated by dividing thedifference of the stable (but decreasing) phase angle from front to backof the Slug, e.g., 60 degrees total, by the number of micropulses in aSlug, e.g., one thousand.;

9. The RF phase control requirement is set by the fractional frequencydifference, for example, one part in ten thousand;

10. RF frequency of each Snugger tank is programmed to stepprogressively to higher frequency, synchronized to the different speedsof the multiple ion species. Practical limits on the bandwidth of thelinac structures and their RF power sources determine the limits on thedifferent Isotopic Species that can be treated by one Snugger beamline;

11. Where another unique group of Isotopic Species is used with a largedifference in mass and speed, e.g., to achieve valuable effects in thefusion fuel target such as Fast Ignition, separate, parallel Snuggersare required. Each separate Snugger is able to treat Isotopic Specieswith mass differences ranging over approximately 10% (i.e., ±5%);

12. Snugging causes the microbunches in a Slug to pass successive pointsalong the beamline at progressively higher frequency, corresponding tothe decreasing distance between microbunches. To maintain efficient useof the applied RF voltage, the RF frequency is correspondingly increasedin a specified number of discrete locations in the Snugger, insuccessive blocks of Snugger linac tanks. Higher frequency RF structureshandle higher electric accelerating fields, substantially shorteningphysical length;

13. Snugging limit is reached when the dimensions of RF structure arejudged to be as small as acceptable to pass the very-high-power beamwith a total beam loss by wall impingement of, for example, 1% over tensof kilometers of beam tube;

14. Slug average current increases, e.g., 10×, for Snugging that isdriven by frequencies starting at 400 Mz and stopped by frequenciesending at 4 GHz. Width of phase on RF Snugger wave is substantiallyunchanged, and microbunch peak current increases by the Snugging factor,i.e., 10× for this example;

15. Snug Stopping returns the microbunches to the same reference energy,as will be required regarding chromatic aberration at the focus. the:enables timing to accommodate different distances to multiple chambers;

16. In the Telescoper accelerator section, Slugs of different isotopesare accelerated to the different energies needed for all isotopes tohave common rigidity. In general, the Telescoper accelerates multipleparallel beams. The multiple parallel beams of each isotopic species arediverted by pulsed switch magnets, located between consecutive tanks ofthe Telescoper section, when the energy of that specie's ions reachesthe specified ratio of momentum to charge state (i.e., magneticstiffness or rigidity) that is identical for all species to enable allspecies to be: 1. transported in the same beamlines without change tothe strength of the magnetic field prior to 2. Telescoping of thedifferent isotopic Slugs into each other as they approach the end of thebeam path to the fusion pellet.

17. Emit multiple, parallel high-energy beams (e.g., 4 beams) from theTelescoper, which is the concluding part of the linear accelerator.

18. Merge multiple beams (e.g., 4 beams) from linac into one beam bystacking them 2×2 in each plane of the transverse phase space. Thisresults in a 4-fold increase in micropulse peak current and Slug peak oraverage current, and a concomitant increase in the beam emittance by thebasic factor of two plus a small dilution factor;

19. Maintain individuality of the merged microbunches throughout thesystem, until released from RF phase focusing in the beamlines leadingto the fusion fuel target in a specific chamber;

20. Reconfigure the Merged single beam into multiple parallel beams in aSlug-Slug Delay Line (SSDL). In one embodiment, the first of twoconsecutive Slugs is switched into the first phase of the SSDL suchthat, at the output of this phase, the previously consecutive, inlineSlugs travel in two parallel beamlines, with micropulses RFsynchronized, micropulse for corresponding micropulse. Repeating thisprocess in the second stage of the SSDL results in the desired number ofparallel beams (e.g., four) at the SSDL output. The micropulses in allthe parallel beamlines (e.g., four) are RF synchronized, micropulses tocorresponding micropulses. In the embodiment treated here, the delay in,and therefore the length of, the second phase of the SSDL is twice aslong as in the first. The magnets that switch selected Slugs into theSSDL are moderately fast, by virtue of the enlongated gaps between Slugsthat results from Snugging. The resultant configuration of four parallelbeamlines is carried throughout the following processes, until focusedonto the fusion fuel pellet;

21. Microbunch structure is maintained by Phase Focusing naturally inthe Main Linac, Snugger, and Telescoper linac structure. In otherportions of the beamlines where the beams do not experience the electricfields of RF acceleration, the microbunch structure is maintained byperiodic Bunch Reflectors (Double Rotators). In standard practice, thetypical use of single Rotation minimizes the momentum spread whilemaximizing the time dimension of a microbunch. Double Rotation, whichaccomplishes Reflection of the longitudinal phase space ellipse in thetime axis, facilitates maintenance of the microbunch structure over longtransport distances by resetting the orientation of the ellipse suchthat a longer distance will be traveled before shearing of thephase-space ellipse in the longitudinal plane requires the nextapplication of Rotation/Reflection;

22. Helical Delay Line 2800 (HDL, a.k.a. Isotope-Isotope Delay Line)removes specified, high fractions from the time gaps between Slugs(e.g., Slug centers move from 2.5 μsec apart to 300 nsec apart);

23. Helical Delay Line 2800 (a.k.a. Isotope-Isotope Delay Line) functionhas the flexibility to remove a variable amount of the time gaps, asrequired by Multiple Chambers;

24. Microbunch identity continues to be maintained by Phase Focusing inthe HDL by periodic Bunch Reflectors/Double Rotators. For largedifferences of the ion (and microbunch) velocity, in particular wherevelocities are used for the Compression Pulse and the Fast IgnitionPulse that are widely different, each of the parallel beamlines in theHDL is bifurcated before entrance to each Bunch Reflector and recombinedinto a common beamline just after exiting the Reflector;

25. Slicking is accomplished in the sections of the beamline that arespecific to one of the multiple reaction chambers. Slicking againprovides differential microbunch speeds between successive microbunchesat a specified distance upstream from each fusion chamber. The amount ofdifferential speed imparted to the microbunches of each Slug is set tocause the microbunches to interpenetrate to form the desiredcontribution to the pulse structure of all isotopic Slugs at the fusiontarget. The distance from the Slicker to the Chamber and Target isapproximately the same for each of the Multiple Chambers; and

26. The beam Wobbler (ref. Golubev), FIG. 16, was conceived to create ahollow beam for the Compression Pulse to heat an annular portion of thecylinder containing the fuel, FIG. 17.

27. Conventionally, the Wobbler's RF field is programmed to cause theannulus heated by the spiraling Compression Pulse (the absorber layer)to follow the imploding radius of the layer of the cylinder's barrelthat works to compress the fuel (the “pusher” layer) (Ref Basko. FIG.18). This improves the efficaciousness of a given amount of beam energyto drive the implosion. The extent of this improvement is limited,however, because the size of the spot (e.g., 1-3 mm) results in heatingmaterial that is more remote from the absorber-pusher interface as wellas the desired material close to the interface.

28. The innovations that reduce the spot size (e.g., 50 μm) amplify thebenefits of following the absorber-pusher interface by causing the beamenergy to be deposited more at the most desirable radius and, therefore,to not continue to deposit heat in material that is more remote from theinterface, and therefore less effective in contributing to the implosiondynamics.

29. In the prior art, the motion of the absorber-pusher interface inwardresults in expansion of the absorber material. This results in reducingthe density of the absorber material with concomitant reduction of itsstopping power, which in turn results in wasting some of some the energyof the ion beam by allowing the affected beam ions to carry some energybeyond the far end of the target.

30. The loss of efficiency by rarefication of the absorber layer isavoided by heating the thinner annulus (e.g., 100 μm with the e.g., 50μm radius spot) near the absorber-pusher interface. Thereby, the beamions encounter target material that has had the least time to expand asthe beam heats the thin annulus just outside the interface while theinterface moves inward.

31. Fast Ignition is accomplished after the fuel has reached peak highdensity, e.g., 100 g/cc. In the prior art (Ref. Basko. FIG. 19), fuelcompression is accomplished by the action of the Compression Pulsealone, and the range of the ions used for Fast Ignition is the same asthat of the ions used for Compression. These ions penetrate farther intothe pre-compressed fuel than needed to bring to ignition temperatureonly the amount of fuel needed to initiate a propagating fusion burn.

32. The innovation of applying the principle of telescoping beams(multiple ion species) allows using ions with shorter range for the FastIgnition pulse as compared to the range of the ions for the Compressionpulse.

33. Because the prior art for cylindrical pellets with Fast Ignitionusing ions with the same range for Fast Ignition and for Compressionresults in heating a larger mass of pre-compressed fuel than needed forFast Ignition, the Fast Ignition beam must carry more total energy bythe same factor. By the same token, the prior art requires the FastIgnition beam to have higher power than required by the fundamentals ofFast Ignition because the Fast Ignition energy must be deposited in thesame amount of time regardless of penetration depth.

34. The basic design requirement for Telescoping is that all ions havethe same magnetic rigidity, which is proportional to βγA/q (b=v/c,c=speed of light, A=atomic mass number, and q=ionic charge number).Because the most favorable charge state is singly charged (due to spacecharge limits in beam transport and ion source design), it is mostlikely that all ions will be in the same, singly charged state. When thesame charge state is used for the different isotopes, the result is thatheavier isotopes will have less energy.

35. In addition, any of the high-energy beam ions (for Compression orthe shorter range ions) will be fully stripped to a charge number equalto the atomic number Z (i.e., q=Z) by interaction with the targetmaterial.

36. Both the lower energy and higher Z of the heavier ions contribute toshortening the range of the ions in the Fast Ignition pulse as comparedto the ions in the Compression Pulse. For example, using xenon (Xe) forthe Compression Pulse and lead (Pb) for the Fast Ignition Pulse, theTelescoping condition is met with ˜13.5 GeV Pb for the Fast IgnitionPulse and 20 GeV Xe for the Compression Pulse. The resulting differencein range is about a factor of seven.

37. The factor of e.g., about seven reduction in range reduces therequired beam power by this same factor of seven.

38. The range of the Fast Ignition ions may be adjusted, withcorresponding adjustment of the range of the Compression ions, tooptimize the parameters of the ion beam to achieve greatest efficiencyof the overall use of beam energy to achieve compression and ignitionwith propagating burn.

39. The benefits of using shorter-range ions, i.e., the part of theoverall driver pulse for which Fast Ignition is the first purpose, maybe exploited most thoroughly by making the duration of the shorter rangepulse longer than needed for the Fast Ignition function alone. Forsimplicity of presentation, therefore, the terms “Fast Ignition pulse”and “shorter-range pulse” may be used interchangeably, particularly fordescription of effects other than the principal one of Fast Ignition.

40. The dynamics of the end caps may be optimized by heating them usingparts of the longer duration beam of shorter range ions (aka FastIgnition). By temporal modulation of the amplitude of the Wobbler's RFfield, these parts of the beam may be caused to hit the target off-axis,and the spot-on-target may be caused to spiral toward the axis as usedin the prior art for the Compression pulse (FIG. 18). The spiraling mayalso combine moving away from the axis, if useful.

41. The additional advantages accruing from the duration of theshorter-range beam being longer than the Fast Ignition time generallyinvolve overlapping the first-arriving portions of the Fast Ignitionpulse with the later-arriving portions of the Compression pulse.

42. By appropriate shaping and timing of the Wobbler's waveform and,therefore, od the Wobble of the beam at the target (i.e., the radialdistance of the wobbling (revolving or swirling) beam spot from the axisof the target), the various portions of the Fast Ignition pulse beforethose designated for Fast Ignition per se may be used to tailorcylinder-end dynamics.

43. One such effect would include generating pressure in the end-capmaterial to resist bulging or blowing out. (FIG. 20) Because the FastIgnition isotopes penetrate much less material, the end closure of thecylindrical target needed to stop them will be accordingly thinner thanthe cylinder barrel is long, and the intensity of heating this materialwill be commensurately higher for a given beam power, modulo the area ofthe end caps that is being heated. The pressure generated will resistthe pressure from inside the cylinder that would drive the ends outward.

44. In addition to resisting bulging or blowing out, the high pressuregenerated in the material of the end caps provides a means to drive theend caps inward. This may be used to combine motion of the end capstoward the mid-plane of the target, along the target's axis, with thebasic radial compression of the cylinder barrel that is driven by thelonger-range ions of the Compression Pulse.

45. Curvature of the end caps together with appropriate wobble of thetarget spot may effect motion, driven by the energy deposited by theshort-range ions, which approaches hemispherical implosion at each endof the target. (FIG. 21). The resulting convergence of the end caps iscoordinated with the cylindrical convergence of the body of thecylinder.

46. The general goal of this combination, and other design uses ofshorter range and longer range ions, is to optimize the overall dynamicsof the target implosion, to achieve the desired density of the fuel massat the location designated for Fast Ignition with the least effort(least energy content and power) from the ion beams.

47. Because of the telescoping of the isotopes that comprise the beamswith shorter-range (for Fast Ignition and additional purposes), the timescale of the beams at the Wobbler is beneficially longer than thetimescale of the Wobble of the beam spot on the target. The longertimescale for modulating the Wobbler's makes the desired modulation ofthe waveform of the Wobbler field technically feasible.

48. Another use of the overall duration of the Fast Ignition pulse beinglonger than needed for Fast Ignition alone concerns fuel or targetmaterial that will have blown outward along the axis during thecompression phase. By timing the arrival of portions of the FastIgnition pulse that are not wobbled to arrive on the axis (and near theaxis) before of the designated time for heating the Fast Ignition fuelmass, the short range beam will burn through material that has blown-outalong the axis. (FIG. 22) Blow-off that is fuel will, in general thismaterial will be at lower density than required for fast ignition, andthe Fast Ignition beam will need to burn through this blow-off to reachthe desired Fast Ignition mass.

49. The processes for burning through the blow-off are generally byheating, which increases the internal pressure and the thermal speed ofthe material. Higher pressure will cause the material to expand,decreasing its density and thereby decreasing the deleterious, prematureslowing that robs energy from the Fast Ignition beam. Higher thermalspeed will accelerate movement of the material out of the way of theFast Ignition pulse.

50. On the axis, the blow off will be primarily fusion fuel escapingthrough the hole provided to admit the Fast Ignition beam. Therefore,besides the direct heating of the blow-off material, theburn-away/burn-through on axis will be aided by fusion reactionsresulting from the Fast Ignition beam heating the blown-off fuel.Although the density of the blown-out fuel will be below that needed toignite propagating burn, the additional heating from the fusionreactions that occur will contribute to driving the blow-off out of thepath of the Fast Ignition beam, allowing it to penetrate to the highdensity fuel designated for Fast Ignition.

51. The various advantages of using ions with significantly differentstopping distances (ranges) in the target involve appropriate timing ofthe RF field in the Wobbler. Slower (and heavier) isotopic species willpass through the Wobbler before the faster (and lighter) species.

52. The largest difference in speed will be between the isotopes in theCompression Pulse and the isotopes of the Fast Ignition Pulse. Forexample, the speeds of 20 GeV xenon ions and 13.5 GeV differ by ˜30%.For this much difference in speed, the Wobbler may be located at aposition upstream from the target where the time gap between the slowerFast Ignition pulse and the faster Compression pulse allows the entireFast Ignition pulse to exit the Wobbler before the RF fields of theWobbler begin to rise.

53. The part of the shorter range beam that heats the fuel mass designedfor Fast Ignition is the last to arrive at the target on the axis andwill therefore not be Wobbled. This may be accomplished by designatingeither the first part or the last part of the pulse of short-rangeisotopes as the Fast Ignition part. Selection of one versus the otherend (slowest or fastest) of the slow isotopes may be beneficial foroptimizing overall driver design.

54. The slowest isotopes will be first through the Wobbler, but thehigher speed of the last isotopes may be used to achieve reversal of theorder of the isotopes during transit between the Wobbler and the target.This would be accomplished by making the transit distance sufficientlylong for the faster isotopes to pass through the slower isotopes as allisotopes are traversing this distance.

55. If the first part of the Fast Ignition pulse is designated forheating the fuel mass for Fast Ignition, the Wobbler's field will be offwhen this first part passes through it.

56. If it is beneficial to designate the last part of the shorter rangeion beams to heat the Fast Ignition fuel mass, the distance from theWobbler to the target will be sufficient to allow the last isotopes tobecome the first to arrive at the target. In this case, the Wobblerfield is off when the last part of the Fast Ignition pulse passesthrough it.

57. The spot of the beam on the target may move radially inward oroutward according to the programming to achieve a radial “rastering”effect, if desired for smoothing the irradiation intensity or for anyother purpose beneficial to optimizing the overall driver design.

58. Also to improve the smoothness and symmetry of heating the end caps,the beam emittance may be purposely made larger for the portion of theshort range (FI) pulse that is used to heat the end caps. By this means,the area that is irradiated at any moment by this beam will be largerthan the small spot desired for fast ignition, e.g., 50 μm, withoutchanging the settings of the elements of the final focusing system onthe beam's necessary nanosecond time scale. The larger spot size wouldadd smoothness and symmetry to the heating, which will help suppress thegrowth of instabilities during the implosion of the end caps.

59. The desired variation of the emittance may be generated at thedriver's Front Ends by appropriately designing the extraction electrodesfor selected ones of the ion sources for the multiple isotopes.

60. If a larger emittance is used for some part or parts of the beam, itwill facilitate achieving high power in the beams by: 1. The scaling ofthe achievable, space-charge limited (Child-Langmuir law) current fromion sources, and 2. The scaling of the space-charge-limited maximumtransportable, beam current (e.g., Maschke, 1976).

61. The beam emittance of the parts of the shorter range beam thatarrive at the end caps of the target at progressively later times willbe progressively smaller, to focus most efficiently on the decreasingradius of the imploding end-caps.

62. During the period just previous to Fast Ignition, when the mainfunction of the shorter range beam is to burn through the blow-off, thebeam emittance will be the smallest value, i.e., that required by thesmall radius of the cylindrical volume containing the fuel mass for FastIgnition.

63. Emittance changes will be in steps, corresponding to designingdifferent isotopic ion sources according to the part of the shorterrange beam that will be provided by these particular sources.

64. The feature of varying the emittance and thereby the spot size mayalso be used for the Compression pulse, if this would add anyperformance advantage for the dynamics of the implosion of thecylindrical barrel.

65. Additional detail may be added to the programming of the Wobblerfield to cause the shorter range ions to impact that target at varyingradial distance from the axis as may provide additional benefits for theoverall compression and ignition processes.

In general, through the effects described in the foregoing, theprogramming of the wobble of the different parts of the Fast Ignitionpulse, in combination with the telescoping of the different isotopesthat make up the overall Fast Ignition pulse, is designed to achieve themost efficient and effective use of beam energy and power for the fuelcompression and ignition processes.

Description and Operation of New Current Multiplication Processes BeamParameters at Linac Output

The parameters that characterize acceleration in the linac follow theprior art, proven by operating machines and established by designs usingstandard, industrial design tools. Total linac output current isincreased by using multiple, parallel, RF-synchonized output beams,e.g., four. Linac output further is increased at the Front End via thewell-known scaling of space-charge limited current with (βy)^(5/3)(β=c=speed of light, and γ is the relativistic parameter), usingestablished ion source and high DC voltage technology as demonstrated bythe Argonne National Laboratory 1977-1980 using a 1.5 MV Dynamitron®.

The new arrangement of current multiplying processes makes strong use ofaccelerating multiple isotopes. The effect of using Multiple Isotopes,alternatively known as “Telescoping Beams”, can be appreciated by addinganother multiplicative factor to the previously existing line-up ofprocesses. However, ramifications of the present approach to exploitingbeam telescoping lead to distinctly different types of currentmultiplier processes than those identified in Equation 1. Occurring inthe driver system “downstream” (after) the linear accelerator, and underthe constraints of the 6-D phase space of each species of beam particleas previously discussed, the different beam restructuring, beamcompaction/intensification/overall current-amplification also favorablyaffect the ultimate focusing on the fusion target, reducing it by afactor ≥10.

New Features after the Main, Fixed Beta-Profile Linac

As shown in the diagram 2300 of FIG. 23, Snugging imparts a differentialvelocity between successive microbunches. Snugging is accomplished byoffsetting the RF frequency of the Snugger from the bunch frequency (therate at which microbunches pass a point on their path) such that thefirst bunch is decelerated most and the last bunch is accelerated themost.

FIG. 24 provides a detailed diagram 2400 depicting the processes ofsnugging 2401 and snug-stopping 2402. FIG. 25 provides an alternatediagram 2500 illustrating differential acceleration by offset RFfrequency.

The microbunches inside each Slug are virtually identical at the inputto the Snugger, which imparts a progressive speed differential amountingto, for example, ±5% to ±10%, to the first and last microbunchesrelative to the unchanged speed of the center bunch. When Snugging hasreached practical technological limits, e.g., clearance between the beamand the surface of the beam tube or electrode, the Snugging process isreversed and the speed differential is removed in the Snug Stopper.

As shown in FIG. 25, the amount of frequency offset is the quotient of(1) the maximum phase shift specified to be experienced between thefirst and last microbunches and (2) the duration of the Slug. Forillustration, taking the Slug to be 1 microsecond long and the totalphase shift to be 60 degrees (⅙ of an RF cycle), the frequency shiftwill be ⅙ MHz. Taking the RF frequency of this Snugger section to be 1GHz (e.g., an accelerating cell length of 12 cm for a v=0.4c ion), thephase control accuracy requirement is about 0.016% or better.

Both differential acceleration and differential deceleration result fromthe Snugger's RF field being offset slightly from the bunch frequency.To add differential velocity to the last half and subtract velocitydifferentially from the first half, the Snugger RF frequency is higherthan the bunch frequency at a given point on the beam path. To removethe differential velocity in the Snug Stopper, the RF frequency is lowerthan the bunch frequency at that point in the beam path.

The Snug Stopper is shorter than the Snugger because its RF frequency ishigher, e.g., 10×, and the higher RF frequency structures support anaccelerating voltage gradient that is higher as approximately defined bythe Kilpatrick limit. For the example of 10× Snugging with equalincrease in RF frequency, the gradient of the Snug Stopper is aboutthree-times higher than in the first section of the Snugger.

As shown in the diagram 2600 of FIG. 26, Slugs are caused to contractaxially inside the Snugger, e.g., by 10×. Entering the Snugger, thedistance from the center of one Slug to the center of the adjacent Slugis the length of a Slug plus an inter-slug space originally set by theMaster Timing. For example, Slugs that are 2.5 μsec long at the Snuggerentrance will be 0.25 μsec long at the Snugger exit.

The empty space that grows between the Slugs in Snugging will besubsequently removed via the Helical Delay Line 2800 (isotope-isotopedelay), as described in sections treating the HDL, and other elementsdownstream from the Snugger.

No net power is added to a Slug by Snugging. Excitation of theaccelerator structure is the primary power requirement. However, beamenergy flows to the RF fields during deceleration, allowingcorresponding reduction of the RF feed power. For the microbunches thatare accelerated, the RF feed power is increased correspondingly tosupply the acceleration energy. A modest part of the shifting energymight be recycled, e.g., from the decelerated bunches to the acceleratedbunches, by RF system design refinements. In sum, however, the energyconsumed by the Snugger including the excitation “copper loss” will be asmall fraction, e.g., 1-5%, of the energy consumed by the primary linearaccelerator.

The efficiency of using the provided RF accelerating field strengthgains when ions experience the amplitude near the peak of the sine wave.In opposition to this argument for using a large excursion of phaseangles is the desirability of a linear progression of the differentialacceleration of successive microbunches. For illustration, nearly linearprogressive increased acceleration/deceleration would restrict the phasewidth to ±30 degrees. A larger phase shift will decrease the peak RFvoltage and/or the length of the Snugger accelerator. The Snugging usesthe rising side of the sine wave, which provides the phase stabilityeffect (phase focusing) that maintains the longitudinal emittance of themicrobunch.

By insertion of RF cavities at harmonics of the basic Snugger frequency,a virtual RF wave may be synthesized with an effectively larger phasewidth to drive the Snugging action.

Cradling also may be incorporated into the control of the RF waveformsto increase the usable phase width in Snuggers and Slickers. TheCradling effect shifts the RF sine waveform to compensate for thecurvature of the sine wave as the differential speeds increase in themicrobunches as the Slug passes through a Snugger, or to a much lesserextent in the Slicker. Control of the waveform for Cradling isintegrated with parameters from detailed design and modeling. Cradlingincreases the efficiency of the Snugger and Slicker accelerators,primarily to reduce cost, although the power used by these components isa small fraction of the total required to run the Driver.

When the Snugging action reaches a technical limit or otherwisedesirable stopping point, the Snug Stopper removes the differentialenergy spread by reversing the differential acceleration process. Aprimary technical consideration is the existence of high power RFsources at the frequencies of the Stopper. Another primary designrestriction is the diameter of the bore tube, which decreases withincreasing RF frequency. For illustration, starting the Snug with a 400MHz RF and stopping the Snug with 4 GHz RF will shorten the Slug by afactor of ten, and transmission through a bore diameter on the order of2 cm.

Snugger Accelerator and RF Accelerator Structures, Frequencies, andBandwidths

Snug

Microbunches enter the Snugger at the bunch frequency emitted by theprevious linac section. The bunch frequency may be the same as the RFfrequency in that section, or an even sub-harmonic, e.g., one-half theRF frequency. The RF frequency of successive sub-sections of the Snuggerincrease to maintain efficient use of the RF waveform (e.g., ≥±30degrees of phase) as the microbunches move closer together. The highestbunch and RF frequency will occur in the Snug Stopper, during theprocess of removing the bunch-bunch speed differences. The highest RFfrequency will be set by considerations such as beam scraping on theapertures, e.g., approximately 2 GHZ to 4 GHz.

Control of the timing and waveform of the Snugger's RF field providesthe sequence of synchronized RF frequencies, which progressivelyincreases in blocks of accelerator sections, to accommodate Slugs withprogressively higher nominal speeds and, therefore, higher bunchfrequencies. The required RF bandwidths correlate with the range of thespeeds of the various Isotopic Species.

One design-optimization trade-off concerns the number of different RFfrequencies used. For any given frequency, individual microbunches movetoward the zero crossing point of the RF waveform, and experience asmaller fraction of the peak accelerating (or decelerating) voltagegradient. By increasing the RF frequency of succeeding Snugger sections,the voltage gradient experienced by the first and last microbunches canbe periodically reset to the original phase angle. Thus, the utility ofmany frequencies is to achieve more efficient use of a length of Snuggerand the RF power that drives it.

The state of the art of accelerator structure and RF power design andmanufacturing makes it practical and economical to use a substantialnumber of discrete frequencies. However, the multiplicity of frequencychanges will experience diminishing returns, and the number of frequencychanges used is a topic appropriate for trade-off studies duringdetailed design.

Control of the waveform for Cradling is integrated with parameters fromdetailed design and modeling.

Snug Stopping

Snug Stopping removes the velocity differential when the process hasreached the practical limit set by the diameter of the bore-tube thatthe beam must pass through. Beam scraping is to be avoided, andsimulations of particle beams are challenged to model beam “halo”,however it is noted that the high quality beams will be focused tomillimeter and submillimeter diameters downstream, albeit by lenses withlarge aperture magnets. The workhorse S-band structure of SLAC's 2-milelinac is an appropriate illustration. The structure's bore is about 2centimeters, which seems ample for clean passage of the heavy ion beam.

Microbunches progressively compress axially to fit similarly on RF waveswith decreasing RF periods. The momentum spread within microbunchesincreases proportionally. This larger momentum spread, however, afterthe microbunches are released from phase focusing after the Slicker (ata later point on the beam path, and potentially after the RF ChromaticCorrector just after the Slicker), they shear in longitudinal phasespace, the phase space ellipses stretch in the time dimension, and theirinstantaneous momentum spread shrinks. This behavior is exploited in thebeam compaction effect of the Slicker, as discussed elsewhere herein.

Telescoper

The multiplicity of isotopes is distinctively greater than the priorart. The internally consistent, end-to-end design is predicated on usingmany isotopes, e.g., ten. When an Isotope reaches the Common Rigidity,that Slug is switched into a Telescoping Beamline, i.e., a beamline inwhich Slugs get closer together as they move downstream toward thefusion target in one of the multiple chambers. Heavier isotopes areswitched out of the Telescoper first. The isotopic masses of themultiple isotopes range approximately ±5%, subject to the bandwidthlimitations of downstream RF beam handling processes.

Timing features of the beam pulse structure are provided by generating aspecified RF waveform that applies to all operations needed to generateeach Ignitor Pulse. Included is the differences needed to accommodatethe different overall distance from the ion sources to the fusion fueltargets in one or another of the Multiple Chambers, arriving accordingto a specified sequence that provides the desired Ignitor Pulse powerprofile. Gated emission of the various Isotopes from their respective iscoordinated with the master RF waveform.

New Features after Acceleration

For illustration, at the linac output, each of four active beam tubesemits 1.25 A.

Merge

The multiple beams exiting the linac are merged in the transverse phasespace (the 4-dimensional phase space including both planes). Thisamplifies the current in a single beam by the number of incoming beams(i.e., beams emitted from the linac), e.g., four. Merging of four beamsinto one beam may be effected in a two-step process: (1) Merge the fourbeams two at a time, in one of the planes of transverse phase space, toresult in two downstream beams, and (2) Merge these two beams into oneusing the other plane of the transverse phase space. Beams may be mergedwith economical use of phase (small emittance dilution), by merging at abeam focus.

Because storage rings are not used in the SPRFD, and therefore theemittance will not be increased by multi-turn injection into storagerings, the Merge (including dilution factor) is the last process thatnecessarily increases the transverse emittance of the beam after itsexit from the linear accelerator, of which the Telescoper is the lastsection.

The transverse emittance after the merge leaves a factor ofapproximately ten to spare in each transverse plane. That is, iftransport over the remaining beamline were perfect, i.e., no emittancegrowth, the radius of the spot on the target would be ten times smallerthan the 50 μm needed for Fast Ignition. An appropriate apportionment ofthis factor of ten is to assign a factor of three to the accumulation ofemittance growth as an unspecified contributions from the expectedimperfections, misalignments, tolerances in the precision of RF fields,and the precision of magnetic fields optimized versus cost. Theremaining approximately factor of three to spare in the transverseemittance is kept as a factor of safety.

This introduces substantial improvement in the tightness of focusing ofthe beams on fusion targets compared to the prior art. Although themaximum peak target heating needed for Fast Ignition is the toppriority, and overall improvements in the efficiency and effectivenessby additional uses of the tighter focus are a second major benefit ofthe reduced beam emittance, an alternative use with cost and chamberdesign benefits would be to give relief to the parameters of the finalmagnetic lens system. As a general guideline for a final design,maximizing beam parameters to minimize risk is prioritized overexploiting potential costs savings. This rule follows the logic of thefirst thermonuclear explosive that the design should be “as conservativeas possible” (Teller and Garwin). Using design innovations to achievecost savings will be applied for design refinements during the build-outphase of the fusion power supply system for the economy.

Slug-Slug Delay Line (A.k.a. Loop Stacking)

The Slug-Slug Delay Line is the complement of the Merge. It completesthe affordable trade of available transverse phase space for a neededreduction in longitudinal phase space.

Slug-Slug Delay sorts successive sections of beam (Slugs) into parallelbeamlines. The microbunches in parallel beamlines are in synchronism, asneeded to maintain correlation for RF structures with multiple bores forthe parallel beams.

The following illustrates a case of Slug-Slug Delay. The structure ofthe beam emitted by the accelerator is specified with each Slugsubdivided into four Sub-Slugs, which are separated by time gaps thatare adequate for the rise-time of switch magnets. The first Sub-Slug isswitched into a beam line that completes a revolution to return theSub-Slug to the vicinity of the input switch, after which it is in aseparate beamline that is parallel to the beamline that carries theunswitched following Slug. These two parallel beams are switched into asecond loop with twice the circumference of the first. After one orbitaround this loop, these two parallel beamlines proceed in parallel tothe two beamlines carrying the following unswitched pair of Slugs.

Beam amplification has been accomplished by investing a portion of theavailability of investable room in transverse phase space that is dueprimarily to the absence of multi-turn injection into storage rings. Thelongitudinal phase space is unchanged in principle, and growth bydilution will be determined by the precision of the RF fields thatmaintain the microbunch structure as the beams travel to the target.

The total instantaneous current of the multiple propagating Slugs hasbeen increased four-fold by the Merge, and the empty space between Slugshas been increased four-fold. The enlarged space represents culminationof the beam manipulations that rearrange the various smaller time gapsinto one continuous gap between isotopic Slugs, which is removed in onelarge chop, performed by the Isotope-Isotope Delay Line (aka HelicalDelay Line 2800, or HDL) and the following reinsertion of the sequencecomprising all isotopic Slugs into a single set of four parallelbeamlines.

The multiple beam configuration (e.g., four) established at the outputof the Slug-Slug Delay continues to the fusion fuel target. The eightSlugs going into the Slug-Slug Delay come out as two sets of Slugs inthe four parallel beamlines. One set of four Slugs is routed to each endof the cylindrical target.

The choice for the location of the Slug-Slug Delay from a number ofpossible positions along the beamline depends on the technologytrade-offs associated with propagating a single beam (viz. after Mergingthe multiple beams from the linac) or as multiple parallel beams (viz.as created by the Slug-Slug Delay, aka Loop Stacking). Thisconsideration is relevant to the beam configuration input to the HelicalDelay Line. FIG. 27 shows a diagram 2700 of the relative length andspacings of slugs, using three species for illustration.

Isotope-Isotope Delay Line (Aka Helical Delay Line, HDL)

Shown in the diagram 2800 of FIG. 28, the effect of the Helical DelayLine 2801 is to chop out a preponderance of the space between centers ofsuccessive Slugs. This achieves a major reduction in overall beamduration, which was made possible by rearranging various gaps into asingle large gap between Slugs in the series of beam manipulationspreviously described, e.g., Snugging moves the multiple small gapsbetween microbunches inside individual Slugs to the gap between Slugs.

After the isotopic Slugs are reinserted in common beamlines (e.g.,four), the gap remaining between the trailing end of one Slug and theleading end of the next, likewise the time between Slug centers, isintentionally variable. This is to accommodate the different amounts oftelescoping that will occur during transit over the different remainingdistances to the Multiple Chambers.

The length of each coil (orbit length) 2803 of the HDL is of the orderof the distance between the centers of successive Slugs. However, timingof the magnets 2804 for switching individual Slugs out of the HDLaccommodates any Slug spacing greater than the time of the orbit aroundthe circumference of one coil of the HDL. The first Slug in a Slug Traintraverses the full length of the Helical Delay Line before its exitpoint. Successive Slugs of progressively faster ions exit the HDLsequentially, after traversing progressively fewer turns of the HDL. Theexits 2805 for the various Slugs are approximately at the same azimuthalpoint on the HDL 2801.

Large fractions of the inter-Slug gaps, including the enlargement of thegaps due to Snugging and the Isotope-Isotope Delay Line, are removedwhen the Slugs exiting the HDL are switched back into the commonbeamlines that continue to the Chambers.

After output from the HDL, the space now between Slugs, afterreinsertion as inline Slugs in the parallel beamlines (e.g., four) thatwill terminate at the mouth of the Final Focus lenses (e.g., four), isspecified by the downstream timing requirements for ignition in one ofthe Multiple Chambers. The Slug-Slug space remaining accommodatessubsequent beam manipulations and beam dynamics, particularly thosemanipulations that operate on individual microbunches within individualSlugs. Examples are Slicking, and potentially RF Chromatic Correction tocounter the contribution of the Slick Kicks, by exploitation of theirinter-correlation, to chromatic aberration at the spot-on-target focus.Microbunch properties (emittances) are maintained by periodic Reflectionof the ellipse of the longitudinal emittance, or distributed phasefocusing up to the Slicker's output, or potentially the output of the RFChromatic Corrector. RF maintenance maintains the longitudinalmicrobunch structure within Slugs.

Slug's Exit Delay Line

The spacing of the microbunches within each Slug is static from the SnugStopper downstream to the Slicker that is in the portion of the beamlinespecific to one or another of the Multiple Chambers. The freezing of themicrobunch spacing uses the Snug Stopper to remove the speed differencebetween microbunches and uses Bunch Maintenance (Reflectors) atintervals along the beamline up to the Slicker. Freezing the microbunchspacing in this way accommodates:

-   -   Different lengths of the paths of different Slugs through the        HDL and    -   Different lengths from the HDL to the Multiple Chambers.

Locating the Snug Stopper upstream from the HDL 2801 removes therelatively large energy spread from microbunch to microbunch that wasinput for the Snug process. This allows the Isotope-Isotope Delay Line(HDL) to transport beam with only the small momentum spread insideindividual microbunches.

Microbunch Maintenance

Maintaining the microbunch structure and preserving the 6-dimensionalphase space of individual bunches is an overall hallmark feature of thenew Driver design.

Beam Drift and Conditioning for Multiple Chambers:

HIF fusion power is most economical if a single heavy ion driver systemignites fusion pulses in a repeating sequence in multiple fusionchambers. In the most general layouts of multi-chamber fusion powerparks, the distance from the accelerator varies from chamber to chamber.

Telescoping and Snugging are the key dynamic beam generation processes.Telescoping first is grossly programmed (bracketed) via appropriatedifferences in the timing of emission from Multiple Isotopic ion sourcesto culminate at Multiple Chambers. The precise timing within the timingbrackets is provided by RF waveform control. Absolute timing of thearrival of a Slug at the target thus is extended to a small fraction ofthe RF period of the lowest frequency RF accelerator. For example,control to 0.01% of the 100 nsec period of a 10 MHz Marquee Linac wouldgive 0.01 nsec control of the Ignitor Pulse Profile. However, thistiming is further refined by the beam handling at the highest RFfrequency, about 2 GHz. RF phase control to 0.01% of the 0.5 nsec periodat 2 GHz translates to timing control to 5 psec. Passing this level ofcontrol along the beamline translates to tightly regulating the beam'sspeed. This translates to tight regulation of the time of arrival of allpieces of the beam at the target for near simultaneity or pulse profileshaping as desired.

Slick

The Snug Stopper permits microbunches within a Slug to maintain theirrelative positions as a Slug traverses the distance to one of theChambers. At a specific location on the beamline before the targetChamber, the differential motion of the microbunches is restarted by theSlick process, which is similar to the RF process for Snugging,differing only in that after the Slick kicks imparts the differentialspeeds, the microbunches are released from phase focusing and the Slickprocess is not terminated and allowed to continue to the target.

At specified distances upstream from each of the Multiple Chambers,Slicking imparts specified, smaller velocity differentials back intomicrobunches of the various Slugs. After the Slicker, the microbunchesare released from the axial length constraint of phase focusing. FIG. 29illustrates the Slicking process 2900. As the Slicked beam drifts towardthe target chamber, the centers of the microbunches get closer togetherand individual microbunches lengthen as a result of the velocity spreadintrinsic in the longitudinal phase space. Space charge forces alsostretch the microbunches, and tend to distort the ends of thelongitudinal phase space ellipses such that the emittance, or momentumspread, that effectively must be focused tends to increase. This spacecharge effect is mainly operative during the initial period beforeconsecutive microbunches start to feel the counteracting space charge ofeach other.

Conserving the longitudinal phase space area, the microbunches stretchin time and narrow in instantaneous momentum spread as the various Slugsproceed, and eventually Telescope into the desired beam power profile atthe fusion target. RF Chromatic Correction may remove part or all of thecontribution to chromatic aberration due to the Slick kicks, but therequired size of the spot-on-target budgets allowable chromaticaberration that will be met without taking advantage of thispossibility.

The differential speeds imparted to the microbunches by the Slick kicksare initially specified so that all microbunches arrive at the targetsimultaneously, or with a desired spacing. Any effects of space chargeto alter the inter-bunch speed differential may be compensated in partby corresponding modulation of the accelerating voltage of the Slicker.Space charge effects and errors in RF waveforms of the bunch maintenanceand the Slick will be responsible for any growth of the longitudinalemittance.

The effective minimum, total momentum spread 3000 is illustrated in FIG.30 for the general case. The potential minimum Slug length is seen byinspection to be the sum of the instantaneous momentum spreads of thestack of Slicked microbunches plus the difference of momentum betweenthe front and the back of one microbunch. This effective minimummomentum spread (illustrated in FIG. 31) is well below the requirementsfor acceptable chromatic aberration at the target. FIG. 32 provides adiagram 3200 illustrating an optimal slicker effect.

Ignitor Pulses are switched from a Trunk Beam Line into beamlines thatterminate in (are specific to) the individual Chambers. Each of theseterminal sections of beamline, two per chamber, requires an individualSlicker. Slick imparts much smaller differential speeds than Snug (<0.5%vs. 5%) and the total of Slickers for all Chambers is a relatively smallpart of the system's cost.

TABLE 1 Illustration of Slick as scaled from prior art HDIIF linac HIFlinac HIF Snug HIF Slick 10 GeV Bi + 20 GeV Xe + 20 GeV Xe + 20 GeV Xe +200 MHz 400 MHz 4000 MHz @4000 MHz @target 5 nsec 2.5 nsec 0.25 nsec0.25 nsec 20 nsec 1.2e−4 1.2e−4 1.2e−3 1.2e−3 1.2e−3 1.5 nsec .75 nsec.075 nsec n/a 9e−6 q_μbunch_peak q_μbunch q_μbunch n/a 1000 I_peakI_peak n/a 9e−3 .075 nsec 10 nsec q_μbunch I_Peak Snugmore

Wobbler

The primary purpose of the RF Wobbler is to swirl the beam spot rapidlyaround a circular spot on the end of an annular stopping region in thecylindrical target. Wobbling/Swirling at ≥1 GHz serves purposes of: 1.Smooth energy deposition density in the target, and 2. Smooth variationof the trace of the spot while varying the amount of wobble to cause thebeam spot to spiral toward (or away from) the target's axis.

The RF Wobbler is located upstream of the final focusing lenses, wherethe beam diameter is small in correspondence with the high-frequencyWobbler's aperture. Where Isotopic Species that have a large percentagespeed difference are used, particularly for the sequential processes ofCompression and Fast Ignition, the block of Slugs for Compression mustexperience the Wobbler effect (for the spot to illuminate an annularshape), while the Wobbler effect must be off when the portion of thebeam for Fast Ignition passes through, so the Fast Ignition pulse willarrive at the center of the target.

A number of beneficial effects accrue from using slower ions for theFast Ignition Pulse compared to the speed of the ions of the CompressionPulse. For Cylindrical Targets in particular, the peak power requiredfor Fast Ignition decreases approximately linearly with the ion range.The range of energy deposition shortens with higher Z (atomic number)and lower kinetic energy. The sensitivity of design optimization to thechoice of ions is not great, and choices of the relative mass of theFast Ignition and Compression ions are driven by the practicalconsideration of immediate availability of the hardware, i.e., known andreadily made ion source technology.

For illustration, volumetric plasma xenon sources is commercialtechnology (ANL used this technology in key current and brightnessdemonstrations 1976-80.) Using xenon at Z=53 for the Compression Pulse,a number of heavier ions are good candidates. If lead is used for the FIions, and 20 GeV is the nominal energy of the multiple xenon isotopesfor the Compression Pulse, the Telescoping Condition requires the energyof the lead isotopes to be in a range near 13 GeV. The shortening of therange in the pre-compressed fuel, of this example, is a factor of 6×-7×.The volume of the FI heated mass of pre-compressed fuel may be made tobe approximately the minimum (spherical) physical volume, containing theminimum mass to be FI-heated. Quantitatively, the reduced FI Pulse peakpower requirement that results from the more optimum depth of the FastIgnition-heated zone is a major reason for confidence in the operabilityof the new Driver (SPRFD) design. Coordinated optimization of theparameters for the Fast Ignition and Compression Pulses will achievesignificant cost avoidance.

For illustration, the spot size required for the Ignitor Pulse Beams isfound from the propagating burn parameter, rho·R, for example 0.5g/cm{circumflex over ( )}2 (a conservative value). For fuelpre-compressed to 100 g/cm{circumflex over ( )}3 (a relatively saferequirement), the radius of the FI-heated spot diameter needs to be atleast 50 μm. Larger spots require more peak ignitor beam power andenergy. Smaller spots require more compression, and higher beambrightness.

The FI spot requirement is approximately a factor of ten tighter thanfor the Compression Pulse, as has been shown by reliable simulations.Prior HIF art held the Compression spot to be achievable, but hard toimprove on. The use of the expanded volume in 6-D phase space providedby using a multiplicity of isotopes, particularly avoiding the emittanceincrease due to multi-turn injection into storage rings, achieves thedesired improvements, and makes the advantages of Fast Ignition safelywithin reach of the technology.

The large difference in speeds between the Compression and Fast Ignitionpulses illustrates the substantial time gap between them at the Wobbler.This gap illustrates the satisfactory timescale of the Wobbler's risetime, as illustrated in FIG. 33. The bandwidth for modulating theWobbler field is indicated by reference to the rise time.

The rise time of the RF Wobbler field is of importance regardingseparate pulses for Compression and Fast Ignition (FI). Wobbling enablesheating an annulus along the axial direction. But the beam energy forFast Ignition per se needs to be delivered on axis, with twoconsiderations: (1) If the total cross-sectional area of thepre-compressed fuel is larger than the minimum set by the propagatingburn parameter, the Fast Ignition beam may be correspondingly off-axis,(2) If, economically, the power of the Fast Ignition pulse may begreater than the optimized minimum, the Fast Ignition pulse may have alarger spot area than the minimum, which may be off-axis and still coverthe optimal minimum area of the end of the mass of precom pressed fuelto be fast ignited.

Target Improvements

Compared to the prior art, the new current multiplying processes resultin improvement of the beam parameters that define the intensity oftarget heating and the target response. Higher total beam energy,reduced spot sizes will increase power deposition density and drivetargets providing higher energy gain from the fusion reactions. Powerdeposition density in the target will increase in proportion to thesquare of the spot diameter. Ignition calculations for fuel targetdesign are planned to exploit these improvements.

Heat deposition uniformity is important for good target performance.Wobbling Telescoping Species smoothes the heat deposition by displacingthe instantaneous spots hit by different Species. Due to their differentspeeds, ions at corresponding points along the different Slugs passthrough the Wobbler at some distance upstream from the target (e.g., 30meters) at different phases of the Wobbler RF field, and ions atdifferent axial positions along a Slug penetrate the heated annulus atdifferent azimuthal points.

During the passage of a Slug through a cylindrical target, a Wobbledbeam flies forward with the fixed shape of a helical coil spring. Thethickness of the coils is the diameter of the beam spot. During passageof this helical shape through the target, the instantaneous heating ateach point in the cylindrical annulus corresponds to the helical shapeof the heat source. Heating of the entire annulus is not instantaneouslyuniform. The time-averaged heating smoothes out over passage of thewhole Slug.

With Telescoping, the helical-spring shape of different Slugs in thetarget is rotated relative to each other, around the common axis. Forillustration, if the SlugTrain timing is specified for all Slugs toarrive at the target simultaneously (or with another specified timing,such as to provide a desirable Ignitor Pulse Power Profile), the tips ofthe different beam helices enter the annulus being heated at differentazimuthal locations. The interspersed helical Slugs of the MultipleIsotopes fit into the helical spaces (the helical pitch minus spotdiameter), netting a smoothing factor improvement equal to the number ofMultiple Isotopes. Different Slugs may be timed for differentoverlapping arrangements.

The stretching of individual microbunches by the Slicker adds a furthersmoothing effect. The ions in a given microbunch differ in speed by,e.g., 0.1%. This results in ions that experience the Wobbler fields atthe same time arriving at the target at different times. The effect isto flatten the cross section of the instantaneous beam.

Important improvements in target performance accrue from the smallerspot size by causing the spot of the Compression beam to follow thedecreasing radius of the interface between the absorber layer and thepusher. Fast Ignition is accomplished with less (e.g., 1/7) as much beamenergy and power in the Fast Ignition (FI) beams by using shorter-range,heavier isotopes for the Fast Ignition pulse than for the CompressionPulse. The shorter-range beam may provide additional advantages byincreasing the duration of the shorter-range relative to the time forFast Ignition per se, while maintaining the same power level, by drivingthe cylindrical end-caps to facilitate fuel compression and by burningthrough material blown off during Compression to reach through thismaterial and heat the fuel mass to be Fast Ignited.

Advantages of New Design

-   -   First single-pass HIF driver to use conventional accelerator        technology;    -   Makes strong use of multi-species for telescoping beams at        fusion target;    -   Eliminates storage rings, removing difficult/expensive technical        issue;    -   Loosens requirement for beam emittance of individual ion        sources; and    -   Reduces aggregate total solid angle of igniter beam input-port        apertures in the walls of the fusion chambers.

New Technical Features

-   -   Multiple fusion chambers with one robust accelerator/ignitor        (2-10 BOE per fusion pulse);    -   sacrificial lithium fuel-charge sabot, neutron moderator,        T-breeder, ultra-high temperature hot working fluid;    -   Lithium droplets and fog sprays muffle blast;    -   Lithium droplets and fog sprays create ultra-fast, inter-pulse,        fusion chamber vacuum pump;    -   Pulsed, very high-flow rate lithium pump (from ˜2 tons up to 10        s of tons per second in earliest chambers)    -   Multi-ion species source hotel;    -   Micro-bunch snugging system preserves RF temporal structure and        timing of ion beam;    -   Delay Line reconfigures intra-isotope beam structure to reduce        momentum spread for focusing on target;    -   Helical, serial-species delay and re-timing line;    -   Fewer beamlines and final focus lenses into fusion chambers;    -   Heat transferred at very high temperature by lithium vapor to        heat exchanger inputs, and not transferred through the chamber        walls, so that chamber structural materials operate at the low        temperature of the lithium returning from heat exchangers, e.g.,        a minimal temperature above (e.g., 25° C.) the melting        temperature of lithium (185° C.) and    -   The potential for direct conversion of fusion energy carried by        both charged particles and neutrons.

Improvements Concerning the Overall System Performance and Cost Include:

-   -   Improved ignitor pulse focusing properties (by exploiting 6-D        phase space of multiple species);    -   More intense target heating, with classical “Bohr” ion stopping        in matter that typifies HIF using RF drivers;    -   More uniform target heating;    -   Ten times more ignitor pulse energy than the National Ignition        Facility;    -   Fast Ignition (FI) with FI ion species chosen to maximize        ignition vigor;    -   Timing for Multiple Fusion Power Chambers;    -   Driver duty factor in Pulsed RF range; and    -   Relieved vacuum requirements.

The new beam processes do not call for multi-turn injection into storagerings. This avoids areas of prior technical concern, significant designeffort, and major hardware demonstrations of issues peculiar to storagerings. Removing these concerns shortens the schedule for HIF by removingthe need for a time-consuming validation project, necessitating hardwarewith size, capabilities, and costs similar to those of the storage ringsand linac that would be used in a power producing system.

Comparison

The new processes may be expressed in terms of a line-up of beammultiplication processes.

I _(target) =I _(source) ×N _(isotopes) ×N _(sources) ×N _(snug) ×N_(slick) ×N _(sides)

For illustration, treating either Compression or FI pulse. Compressionparameters shown in Table 2, herein below

TABLE 2 I_(source) xenon with 1.5 MV Preaccelerator voltage =0.1 AN_(isotopes) number of sources per Source Hotel =10 N_(sources) =numberof beam channels in Source =32 Hotels, Preaccelerators, and MarqueesN_(snug) =ratio of microbunch spacing pre- and =10 post-Snug N_(slick)=length of Slug at Slicker ÷ length of =12.5 Slugs at target N_(beams)=number of beams into chamber =8 I_(target) =total beam on target fromall directions =128,000 A Total Power =I_(target) × Ion Energy (20 GeV)=6.4 PW

Increasing the total current out of the linac results in the linac's RFpower being on a relatively short time per ignition pulse, e.g., 300microseconds. Using ten pulses per second, e.g., to drive ten MultipleChambers at one pulse per second each, the RF duty factor is 0.003,safely inside the range classified as pulsed RF power. The benefits ofpulsed RF are higher peak power per source and lower cost per peak-powerWatt.

The new set of processes for compacting the current produced by thelinac minimizes the time the beam dwells in any section of the beamtube, and achieves the important case of a single pass system.Generating the pulse in a minimum of time increases the required RF peakpower, but reduces the RF duty factor below the threshold of a fractionof 1%, where peak RF power costs substantially less peak Watt thancontinuous RF power. For purposes of illustration, Table 3 illustratesthis cost consideration based on engineering estimates scaled from stateof the art HIF design and costs in the current state of the art of RFpower systems:

TABLE 3 Linac current Peak Ignitor Beam Ontime/ Rep Duty Price/ AveragePrice/ total K.E/ion RFpower energy load pulse rate factor W-peak powerW_avg HIF 5 A 20 GeV 100 GW 20 MJ 0.9  300 μs 10 pps 0.3% .015$/W 300 MW30$/W HIDIF .4 A 10 Gev   4 GW  4 MJ .6 1500 μs 50 pps c.w. N/A 400 MW30$/W

With 5 A at 20 GeV, the RF feeds 100 GW into the beam during the pulse.The power to excite the accelerator is a factor of several less than thebeam power, but is not shown. With this caveat, the illustration isinstructive for consideration of the economics of HIF power production.

The new design features exploit the large increase in the total 6D phasespace made available by the use of Multiple Isotopes. The smallest areathat can be illuminated at the surface of the target and, therefore, thesmallest volume into which the beam energy can be deposited, is governedby the conservation law of physics known as Liouville's Theorem. Theessence of Driver design is to work with the 6D phase space defined atthe point of origination of the entire number of beam ions, which totalabout 10 peta-particles, ten million billion, for each Ignitor Pulse.

HIF Driver designs in the prior art are considered stressed, in terms ofthe capabilities of known technology. Characteristically, the stress isexpressible by pressure to achieve the highest brightness of ionsources, to put the required number of ions into a small enough volumeof 6D phase space, so that the processes that constitute Ignitor Pulsegeneration deliver the beam parameters to the fuel target that ignitioncalls for.

Transverse emittance benefits the most, by avoiding the large increaseof emittance attendant on multi-turn injection into storage rings, andlimiting stacking in transverse phase space to a factor of two in eachtransverse plane in the Merge. The factor, e.g., 2.5× (includingdilution), by which transverse emittance grows in each plane, as aresult of Merging multiple beams emitted by the Linac, is the only oneof the series of beam conditioning processes that employs the transverse(4D) phase space.

Smaller transverse emittance enables achievement of smaller beam spotson the target, which increases heating intensity as the inverse of thediameter squared. For illustration, a spot diameter five times smallerwill increase the intensity twenty five times. Preservation of themicrobunch structure and integrity in phase space offers, in principle,to deliver the smallest emittances to the target promised by a heavy ionfusion driver with beam parameters that are very conservative(significant margin of safety).

The Snug and Slick effects capitalize on microbunch maintenance toconserve longitudinal phase space by systematically moving inter-bunchspaces to the adjacent inter-Slug spaces, which subsequently are largelyremoved (according to pulse timing specifications) by the Helical DelayLine. This process compacts the beam without damaging the longitudinalemittance, resulting in lower chromatic aberration at the target.

Generation of Ignitor Pulses by a single pass through the system relaxesthe vacuum requirements. This avoids cost and adds safety margin to thedesign. The new beam processes do not call for multi-turn injection intostorage rings. This avoids areas of prior technical concern, significantdesign effort, and major hardware demonstrations of issues peculiar tostorage rings. Removing these concerns shortens the schedule for HIF byremoving the need for a time-consuming validation project, necessitatinghardware with size, capabilities, and costs similar to those of thestorage rings and linac that would be used in a power producing system.

For an illustrative comparison to the prior art, the new Driver conceptcombines 5-10× higher total Ignitor Pulse energy (or more); as high orhigher total Ignitor Pulse power; smaller spot sizes on targets able toachieve Fast Ignition and improve overall implosion efficiency andeffectiveness; appropriate pulse power shaping at the target; FastIgnition that is optimizable by choice of Ion Species for the Slugs inthe Fast Ignition Pulse; and beneficial treatments of the dynamics ofthe end caps of cylindrical targets (preventing the end caps fromblowing out and causing them to implode, and assisting the Fast Ignitionpulse to burn through extraneous material along the target axis), byextending the on-time of the shorter range ions used for Fast Ignition.

The raised confidence in reliable fusion ignition and burn carries overto all of the alternative applications of achieving massive quantitiesof fusion reactions, including: commensurately stronger confidence inthe less-demanding production of commercial power that accrues bymultiplying the fusion energy output by driving sub-critical fissionpiles; using the output of fusion neutrons to destroy high-level and/orlong lived radioactive wastes, including integration of wastedestruction with additional power from fission reactions; and extremelyhigher fluxes of neutrons in beams for various purposes.

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments thereof. It will, however,be evident that various modifications and changes may be made theretowithout departing from the broader spirit and scope of the invention asset forth in the appended claims. The specification and drawings are,accordingly, to be regarded in an illustrative sense rather than arestrictive sense.

1. A power system, comprising: a particle accelerator system comprising:a source assembly for emitting a stream of isotopic slugs, each slugcomprising a train of microbunches; at least one RF (radio frequency)accelerator section for receiving said slug stream and focusing,accelerating, and funneling said slug stream until a plurality ofhigh-current, parallel slug trains emerges; a telescoper for receivingsaid plurality of high-current parallel slug trains and emittingdifferent isotopic species into a single common-rigidity beamline sothat said species arrive at a target in a specified sequence; at leastone snugger for receiving said common-rigidity beamline and snuggingslugs within said common-rigidity beamline until they drift to points atprescribed distances from at least one target in at least one reactionchamber; a delay line for rearranging beam slugs to collect smallindividual spaces between slugs and sort slugs into parallel beamlinesto produce a smaller momentum spread at focusing on the target; a delayline for eliminating at least a portion of a distance between centers ofsuccessive slugs; a controller for controlling arrival of said slugs attargets in specified reaction chambers according to a specifiedschedule; at least one slicker for imparting specified velocitydifferentials into microbunches of said slugs at specified distancesupstream from each of said reaction chambers; a wobbler for swirling abeam spot rapidly around a target to heat an annular region of thetarget with smooth energy deposition density in said target; and atleast one set of final focusing lenses for focusing said beam on saidtarget; a reaction vessel, comprising within said reaction vessel, alithium body for receiving at least one fuel pellet therein, saidlithium body defining at least one channel for delivering at least oneenergy pulse to said fuel pellet; a system for delivering liquid lithiumto an interior of said reaction vessel in at least one of the forms of:jets and sprays to diminish blast forces and provide neutron shielding;as sheets that rupture immediately after each fusion pulse but reform into act as curtains that reduce backflow of the low pressure gasesreleased by each fusion pulse; and as thick layers flowing along theinner chamber surface in a helical path toward the ends of thecylindrical chamber; and a controller for regulating flows of saidliquid lithium; a plurality of entrance ports penetrating said reactionchamber; and a plurality of beamlines for delivering pulses of heavy-ionbeams to said reaction chamber from said driver, wherein said pluralityof beams enters said reaction chamber through said plurality of entranceports and contacts said fuel pellet through said at least one channel;at least one power plant coupled to said at least one reaction chamberby means of a heat exchanger system, wherein energy generated in saidreaction chamber is transferred to said power plant through said heatexchanger system for conversion to other forms of energy; and a systemfor direct conversion of energy that results from raising the lithium toa plasma state, said system for direct conversion of energy including:components for magnetic piston direct conversion coupling to pick-upelectrodes integrated into said reaction chamber inside a vacuum wall;transmission lines to conduct electricity thus picked up as pulses; anda supply for a magnetic field supplied by magnets outside the vacuumwall.
 2. The system of claim 1, wherein said heavy-ion beams compriseeight heavy-ion beams total, with four heavy-ion beams being deliveredto each of two entrance ports.
 3. The system of claim 1, wherein a pulsecomprises one of: a compression pulse; and a fast ignition pulse.
 4. Thesystem of claim 1, further comprising: an ion source manifold forenclosing said ion source assembly until an inter-microbunch spacing andinter-slug spacing prescribed for each isotopic slug is reached; a delayline that eliminates at least a portion of a distance between centers ofsuccessive slugs; said slugs drifting to points at prescribed distancesfrom at least one target in at least one reaction chamber; a centralcontroller and timing actuators in the ion sources and RF power systemsfor controlling arrival of said slugs at fuel targets in specifiedreaction chambers according to a specified schedule; at least oneslicker for imparting specified velocity differentials into microbunchesof said slugs at specified distances upstream from each of said reactionchambers; a wobbler for swirling a beam spot rapidly around a fueltarget for purposes of smooth energy deposition density in said fueltarget; and at least one final focusing lens for focusing said beam on afuel target; a plurality of beamlines for delivering pulses of heavy-ionbeams to said reaction chamber from said driver, wherein said pluralityof beams enters said reaction chamber through a plurality of entranceports and contacts said fuel pellet through said at least one channel; asub-critical configuration for enclosing a large-fraction of thereaction chamber with fission materials and means for removing heatgenerated in said sub-critical fission pile; a direct conversiongenerator for coupling at least one electrical generator using directconversion of thermal to electric energy from ultra-high temperaturethermodynamic working fluids, said direct conversion generatorcomprising units using either or both non-contacting and contactingenergy conversion means; a heat exchanger system for coupling at leastone power plant to said at least one reaction chamber; said heatexchanger system transferring energy generated in said reaction chamberto said power plant; and means for converting said transferred energy toother forms of energy.
 5. A method of producing neutrons from reactionsfor production of quantities of desirable isotopic materials sandgeneration of neutron beams for research and medical applications,comprising: emitting a stream of isotopic slugs in parallel channelsfrom a manifold holding multiple ion sources, each ion source in saidmanifold producing one of a series of distinct isotopes, the ion sourcefor each slug being timed so that the slugs of said stream penetrate aplane perpendicular to their paths in a programmed time sequence;coordinated groups of parallel slugs entering a high voltage directcurrent accelerating column comprising a plurality of electrodes, eachprovided with an individual aperture for each isotopic slug, theplurality of apertures having the same hole pattern as the manifoldsource; each coordinated group of parallel slugs entering a radiofrequency (RF) linear accelerator having a first section of RFaccelerator converting constant current slug pulses into slug pulsescomprising microbunches, said microbunches passing a point at the RFfrequency; each coordinated group of parallel slugs of microbunchesentering a second RF linear accelerator section, electrode surfaces ofsaid second RF accelerator section providing individual channels foreach of said isotopic slugs; receiving each coordinated group ofparallel slugs into a manifold of magnetic beamlines, said beamlinesrouting each of the individual slugs to one of a series of magneticswitches on a common centerline, switching the sequence of parallelbeams into one collinear train of slugs having a programmed sequence ofspaces; receiving said slug stream in further sections of RF acceleratorand focusing, accelerating, and funneling said slug streams from amultiplicity of parallel manifold sources, wherein a total number ofsaid streams from multiple manifold sources is decreased until apredetermined plurality of high-current, parallel slug trains emerges;by means of a telescoper, receiving said plurality of high-currentparallel slug trains and accelerating isotopic slugs by a multiplicityof energy gains, the energy gain of each slug bringing that slug to amagnetic rigidity that is equal for all isotopic species; switching eachset of parallel slugs out of the telescoper at the points where theyrespectively reach the equal magnetic rigidity; routing each equalrigidity slug into a common beamline with magnetic switches, andemitting a train of slugs having programmed sequencing in time, andemitting trains of slugs in parallel beams, onto remaining processes, sothat said different isotopic species within the trains of slugs arriveat a target in a specified sequence; by means of a merger, receivingsaid plurality of high-current parallel slug trains, into a plurality ofmagnetic beamlines that route the slug trains to a plurality of magneticswitches, the combination of said magnetic switches injecting theplurality of high-current parallel slug trains in RF-synchronizedsimultaneity into a common centerline; wherein injection into the commonbeamline uses equally planes of two transverse phase spaces, withmagnetic transport that minimizes inessential growth in the total phasespace occupied by the merged beams; receiving said common-rigiditybeamline in at least one snugger and snugging the microbunches inindividual slugs within an RF snugging accelerator section and lengthsof said common-rigidity beamline, the frequency of said RF snuggingaccelerating section controlled to provide differential speeds to themicrobunches within a slug so that the microbunches snug and the slugscontract in the beam direction until they reach an inter-microbunchspacing prescribed for each isotopic slug; receiving said trains ofslugs with said spacing in at least one RF snug stopper, removing theinter-bunch speed differentials by the RF snug stopper, whereinfrequency and amplitude of said RF snug stopper accelerating sectionsare controlled to reduce the speed differentials between microbuncheswithin a slug in an orderly manner to minimize inessential growth in thevolume occupied in a 6-d phase space so that microbunch snugging andslug contracting progressively decrease until they reach aninter-microbunch spacing and inter-slug spacing prescribed for eachisotopic slug; eliminating at least a portion of a distance betweencenters of successive slugs by means of a delay line; said slugsdrifting to points at prescribed distances from at least one target inat least one reaction chamber; controlling arrival of said slugs at fueltargets in specified reaction chambers according to a specified scheduleby means of a central controller and timing actuators in the ion sourcesand RF power systems; imparting specified velocity differentials intomicrobunches of said slugs at specified distances upstream from each ofsaid reaction chambers by means of at least one slicker; swirling a beamspot rapidly around a fusion fuel target, for purposes of smooth energydeposition density in said fuel target using a wobbler; and focusingsaid beam on a fuel target by means of at least one final focusing lens;delivering pulses of heavy-ion beams to said reaction chamber from saiddriver by means of a plurality of beamlines, wherein said plurality ofbeams enters said reaction chamber through a plurality of entrance portsand contacts said fuel pellet through said at least one channel;enclosing suitable portions of the reaction chamber with materials to betransmuted to quantities of desirable isotopes, and providing means toremove the heat generated in said materials and their transmutationproducts; and providing collimators to form the flux of neutrons intochannels for conduction to target areas for research, small-scalematerial transmutation operations, and medical applications.